MACK FA(W)

FRONT AXLE AND

STEERING SYSTEM
SERVICE MANUAL
OCTOBER 2006
(REVISED)
12-101
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 MACK FA(W) FRONT AXLE AND
STEERING SYSTEM SERVICE
MANUAL
1

(REVISED OCTOBER 2006 — SUPERSEDES ISSUE © MACK TRUCKS, INC. 2006

DATED APRIL 2006) 12-101
 ATTENTION
The information in this manual is not all inclusive and
cannot take into account all unique situations. Note that
some illustrations are typical and may not reflect the
exact arrangement of every component installed on a
specific chassis.

The information, specifications and illustrations in this

publication are based on information that was current at
the time of publication.

No part of this publication may be reproduced, stored in a

retrieval system, or be transmitted in any form by any
means including electronic, mechanical, photocopying,
recording or otherwise without prior written permission of
Mack Trucks, Inc.

Page ii
TABLE OF CONTENTS

TABLE OF CONTENTS

Page iii
 TABLE OF CONTENTS
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SAFETY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Advisory Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Service Procedures and Tool Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
EXPLANATION OF NUMERICAL CODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
ABOUT THIS MANUAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
VISUAL IDENTIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
FRONT AXLE AND STEERING IDENTIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Pivot Centers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Steering Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
DESCRIPTION AND OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
FRONT AXLE AND STEERING INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Steering Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Troubleshooting Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
FRONT AXLE AND STEERING TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Preliminary Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Hydraulic Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
TROUBLESHOOTING CHARTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
POWER STEERING SYSTEM HYDRAULIC TESTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Power Steering Pump Model Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Steering Gear and Pump Flow Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Fluid Foaming Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Power Steering Pump Performance Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Power Steering Gear Internal Leakage Flow Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
VEHICLE INSPECTIONS AND MEASUREMENTS FOR SHIMMY AND RESONANT RIDE . . . . . 51
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Identify the Complaint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Inspections and Measurements Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Vehicle Inspections and Measurements Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Ride/Handling/Steering Evaluation Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
STEERING SYSTEM MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Steering Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Steering Gear Bleed Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Power Steering Hoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Kingpin Lubrication Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
REPAIR INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
STEERING SYSTEM GENERAL INSPECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Steering (Turning) Angle and Turning Radius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Steering Linkage (Cross Steering Tube, Drag Link and Steering Levers) . . . . . . . . . . . . . . . . . 69
Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Steering Knuckle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Axle Center Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Front End Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Page iv
 TABLE OF CONTENTS
FRONT AXLE AND STEERING ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Knuckle Stop Bolt Adjustment (Turning Circle) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
STEERING GEAR RELIEF POPPET ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
TRW/TAS Series Power Steering Gear Relief Poppet Adjustment . . . . . . . . . . . . . . . . . . . . . . 73
Sheppard Power Steering Gear Relief Poppet Adjustment (Manual-Type) . . . . . . . . . . . . . . . . 74
Sheppard Power Steering Gear Relief Poppet Adjustment (Automatic-Type) . . . . . . . . . . . . . . 75
STEERING GEAR ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Steering Gear Adjustments Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Steering Gear Centering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
STEERING KNUCKLE MEASUREMENTS AND ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . 82
Kingpin Lateral Play (FAW 12, 14.3, 16, 18[W], and 20[W] Axles) . . . . . . . . . . . . . . . . . . . . . . 82
Steering Knuckle Vertical Clearance (FAW 12, 14.3, 16, 18[W], and 20[W] Axles) . . . . . . . . . . 84
Steering Knuckle Bearing Adjustment (FA 23 Axles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
STEERING KNUCKLE OVERHAUL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Disassembly — FAW 12, 14.3, 16, 18(W) and 20(W) Front Axles . . . . . . . . . . . . . . . . . . . . . . 87
Disassembly — FA 23 Front Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Reassembly — FAW 12, 14.3, 16, 18(W) and 20(W) Front Axles . . . . . . . . . . . . . . . . . . . . . . . 90
Reassembly — FA 23 Front Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Reaming Knuckle Bushings — FA23 Front Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
PITMAN ARM REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
TRW/TAS Steering Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Sheppard Steering Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
PITMAN ARM INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
TRW/TAS Steering Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Sheppard M100P Steering Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Sheppard 292, 392, 492 and 592 Steering Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
STEERING GEAR REPAIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Steering Shaft Support Bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
STEERING GEOMETRY CHECKSHEET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
FRONT AXLE AND STEERING SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
FRONT AXLE SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
TORQUE REQUIREMENTS AND PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Steering Wheel Retaining Nut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Steering Shaft Bearing Set Screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Steering Shaft Universal Joint Pinch Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Pitman Arm Retention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Drag Link to Pitman Arm Pinch Bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Drag Link, Steering Cross Tube and Booster Cylinder Clamp Pinch Bolts . . . . . . . . . . . . . . . 111
Drag Link Ball Socket Stud Nut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Steering Gear Mounting Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Power Steering Pump Gear Retaining Nut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Hose Fittings (SAE O-Ring Boss Fittings) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
STEERING COMPONENT TORQUE CHART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
SPECIAL TOOLS & EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
SPECIAL TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Special Tools for Front Axle and Steering Repairs and Testing . . . . . . . . . . . . . . . . . . . . . . . 116
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Page v
 NOTES

Page vi
INTRODUCTION

INTRODUCTION

Page 1
 INTRODUCTION
SAFETY INFORMATION

Advisory Labels
Cautionary signal words (Danger-Warning-Caution) may appear in various locations throughout this
manual. Information accented by one of these signal words must be observed to minimize the risk of
personal injury to service personnel, or the possibility of improper service methods which may damage
the vehicle or cause it to be unsafe. Additional Notes and Service Hints are used to emphasize areas of
procedural importance and provide suggestions for ease of repair. The following definitions indicate the
use of these advisory labels as they appear throughout the manual:

Danger indicates an unsafe practice that could result in death or serious

personal injury. Serious personal injury is considered to be permanent injury
from which full recovery is NOT expected, resulting in a change in life style.

Warning indicates an unsafe practice that could result in personal injury.

Personal injury means that the injury is of a temporary nature and that full
recovery is expected.

Caution indicates an unsafe practice that could result in damage to the product.

Note indicates a procedure, practice, or condition that must be followed in order for
the vehicle or component to function in the manner intended.

A helpful suggestion that will make it quicker and/or easier to perform a procedure,
while possibly reducing service cost.

Page 2
 INTRODUCTION
Service Procedures and Tool Usage
Anyone using a service procedure or tool not recommended in this manual must first satisfy himself
thoroughly that neither his safety nor vehicle safety will be jeopardized by the service method he selects.
Individuals deviating in any manner from the instructions provided assume all risks of consequential
personal injury or damage to equipment involved.

Also note that particular service procedures may require the use of a special tool(s) designed for a
specific purpose. These special tools must be used in the manner described, whenever specified in the
instructions.

1. Before starting a vehicle, always be seated in the driver’s seat, place the
transmission in neutral, apply the parking brakes, and push in the clutch
pedal. Failure to follow these instructions could produce unexpected
vehicle movement, which can result in serious personal injury or death.
2. Before working on a vehicle, place the transmission in neutral, set the
parking brakes, and block the wheels. Failure to follow these instructions
could produce unexpected vehicle movement, which can result in serious
personal injury or death.

Engine-driven components such as Power Take-Off (PTO) units, fans and fan
belts, driveshafts and other related rotating assemblies, can be very
dangerous. Do not work on or service engine-driven components unless the
engine is shut down. Always keep body parts and loose clothing out of range
of these powerful components to prevent serious personal injury. Be aware of
PTO engagement or nonengagement status. Always disengage the PTO when
not in use.

Do not work under a vehicle that is supported only by a hydraulic jack. The
hydraulic jack could fail suddenly and unexpectedly, resulting in severe
personal injury or death. Always use jackstands of adequate capacity to
support the weight of the vehicle.

Before towing the vehicle, place the transmission in neutral and lift the rear wheels
off the ground, or disconnect the driveline to avoid damage to the transmission
during towing.

REMEMBER,
SAFETY . . . IS NO ACCIDENT!

Page 3
 INTRODUCTION
Mack Trucks, Inc. cannot anticipate every 앫 Use hoists or jacks to lift or move heavy
possible occurrence that may involve a potential objects.
hazard. Accidents can be avoided by recognizing
앫 NEVER run engine indoors unless exhaust
potentially hazardous situations and taking
fumes are adequately vented to the outside.
necessary precautions. Performing service
procedures correctly is critical to technician safety 앫 Be aware of hot surfaces. Allow engine to
and safe, reliable vehicle operation. cool sufficiently before performing any
service or tests in the vicinity of the engine.
The following list of general shop safety practices
앫 Keep work area clean and orderly. Clean up
can help technicians avoid potentially hazardous
any spilled oil, grease, fuel, hydraulic fluid,
situations and reduce the risk of personal injury.
etc.
DO NOT perform any services, maintenance
procedures or lubrications until this manual has 앫 Only use tools that are in good condition,
been read and understood. and always use accurately calibrated torque
wrenches to tighten all fasteners to specified
앫 Perform all service work on a flat, level
torques. In instances where procedures
surface. Block wheels to prevent vehicle
require the use of special tools which are
from rolling.
designed for a specific purpose, use only in
앫 DO NOT wear loose-fitting or torn clothing. the manner described in the instructions.
Remove any jewelry before servicing
앫 Do not store natural gas powered vehicles
vehicle.
indoors for an extended period of time
앫 ALWAYS wear safety glasses and protective (overnight) without first removing the fuel.
shoes. Avoid injury by being aware of sharp
앫 Never smoke around a natural gas powered
corners and jagged edges.
vehicle.

Aftermarket steering wheels MUST NOT be installed on vehicles equipped with the
MACK RSA (Bendix® ABS-6 Advanced with ESP®). Only OEM-supplied
replacement steering wheels should be used. During any service procedure that
involves reinstallation or replacement of the OEM steering wheel, use care not to
crush or damage the steering angle sensor.

Page 4
 INTRODUCTION
EXPLANATION OF GROUP 400 — STEERING, AXLES, WHEELS
AND TIRES, DRIVELINE
NUMERICAL CODE
GROUP 500 — BRAKES, AUXILIARY
The organization of MACK service manuals has SYSTEMS
been upgraded to standardize manual content
according to a reference system based on GROUP 600 — CAB, TRUCK BODY
component identification. The new reference
system will help link the information contained in GROUP 700 — ELECTRICAL
this publication with related information included
in other MACK service/warranty publications, The second two digits of the three-digit code are
such as associated service bulletins, warranty used to identify the system, assembly or
manuals, and MACK Service Labor Time subassembly, as appropriate, within each of the
Standards. groupings. The codes applicable to this
publication are shown at SECTION HEADINGS,
The system is based on a numerical code, the as necessary, and may also appear in the TABLE
first digit of which identifies the general OF CONTENTS, to guide you to specific
component grouping as listed here: component information.
GROUP 000 — INSPECTIONS Additionally, a two-character alpha code (i.e.,
[CV] GEAR ASSEMBLY, STEERING) is shown
GROUP 100 — CHASSIS with each operation. This alpha code, in
combination with the three-digit Group number,
GROUP 200 — ENGINE identifies the specific assembly, subassembly or
part, and directly relates to the first five positions
GROUP 300 — CLUTCH, TRANSMISSION, of the operation code listed in MACK Service
TRANSFER CASE AND PTO Labor Time Standards.

Numerical Code

Page 5
 INTRODUCTION
ABOUT THIS MANUAL
This manual is intended to provide the technician Whenever a vehicle is jacked up, use proper
with the information required to properly service heavy-duty axle stands under the chassis to
and repair MACK front axle and steering system prevent serious personal injury, death, or
components. The information in this manual is vehicle damage, in the event of jack
divided into eight major sections: Introduction, malfunction or vehicle tipping. Be especially
Visual Identification, Description and Operation, cautious when working on a vehicle having an
Troubleshooting, Maintenance, Repair air suspension system. If the air is exhausted,
Instructions, Specifications, and Special Tools or leaks from the air suspension system while
and Equipment. the parking brake is applied, the front of the
vehicle may move forward as the chassis
Mack Trucks, Inc. has improved this Front Axle settles. Proper precautions must be taken in
and Steering System Service Manual, with this situation, such as exhausting the air from
changes to both content and organization. This the suspension to allow settling before the
manual has been revised to reflect changes and vehicle is raised and supported with
improvements in the vehicle’s front axle and jackstands.
steering system components.

For information concerning chassis alignment

procedures, refer to the Frame, Axle and
Suspension Service and Total Vehicle Alignment,
14-103. Current axle alignment specifications can
be found in the Maintenance and Lubrication
Manual, TS494.

This manual should be read carefully before

attempting to overhaul or otherwise handle,
use, or service the product. Failure to follow
the directions and instructions in this manual
could result in severe personal injury or
death, or property damage. This manual is not
all inclusive, and cannot take into account all
unique situations.

Page 6
 INTRODUCTION

Certain chassis models may be equipped with the As a general proposition, neither Mack Trucks,
Bendix® ABS-6 Advanced with ESP® (Electronic Inc. nor the manufacturer of the front axles,
Stability Program) system, the foundation for the recommends the straightening of bent parts of
MACK RSA (Road Stability Advantage) System. the front axle. Mack Trucks, Inc. is aware,
This system utilizes information supplied to the however, that front axles and components are
electronic control unit (Bendix® Advanced repaired in the field by owners and operators of
EC-60™) from various sensors such as a the vehicles, in order to minimize downtime and
steering angle sensor, yaw rate/lateral expense. Mack Trucks, Inc. does not herewith
acceleration sensor, brake application sensors assume any liability or responsibility for any
and load sensors, to aid the driver in maintaining repairs performed on front axles, including repairs
vehicle control during potential roll-over or to related steering components, by any other
jack-knife events. Because this system relies on party than Mack Trucks, Inc. It is in this context
a specific “parameter set” which is programmed that Mack Trucks, Inc. sets forth the following
into the ECU and is based on vehicle design and procedures in this publication, relating to the
componentry, it is important that a steering angle repair of front axles and components. The
sensor calibration be performed following such procedures in this publication, therefore,
services as vehicle alignment, or after represent suggested procedures only. In the
replacement of certain components such as the event that repairs to the front axle have been
front springs, front spring hangers, king pins and performed, in the judgment of Mack Trucks, Inc.
bushings, steering gear, steering column, in an improper manner, the warranty if any,
steering shafts, drag link, cross steering tube applicable to such front axle and components,
and/or ball sockets. Additionally, a steering angle may be voided thereby.
calibration must be performed if the steering
column has been disconnected from the steering
gear or the steering linkage disconnected from
the steering gear. For chassis equipped with this
system, changes MUST NOT be made to the The illustrations contained in this publication are
maximum steering angle, steer axle track width typical, and not necessarily exact. They are
and/or drive axle track width. For information based on current production MACK components,
concerning this system, refer to the Bendix® and information on other manufacturer’s
Service Data Sheet SD-13-4869, which can be components is included only for reference
obtained online by visiting the Bendix purposes. When working on a vehicle, the
Commercial Vehicle Systems website at technician may find small differences between
www.bendix.com. the vehicle being serviced and the illustrations
provided.

Aftermarket steering wheels MUST NOT be

installed on vehicles equipped with the MACK
RSA (Bendix® ABS-6 Advanced with ESP®).
Only OEM-supplied replacement steering wheels
should be used. During any service procedure
that involves reinstallation or replacement of the
OEM steering wheel, use care not to crush or
damage the steering angle sensor.

Page 7
 NOTES

Page 8
VISUAL IDENTIFICATION

VISUAL IDENTIFICATION

Page 9
 VISUAL IDENTIFICATION
FRONT AXLE AND STEERING The power steering systems utilize pumps that
may be either two-line or three-line pumps. The
IDENTIFICATION pump draws fluid from the reservoir and supplies
fluid flow to the steering gear(s). Fluid is then
Axles returned to the reservoir through the gear(s). The
two-line and three-line systems are basically the
same, with the three-line system having an
MACK axle model designations reflect the axle additional bypass return line from the pump to the
rating (in thousands of pounds) in the reservoir. Typical single gear steering systems
designations. The following is a list of the new with two-line and three-line pumps are shown in
and old axle designations. Figure 1 and Figure 2.
1
Axle Model Weight Rating
FAW12 12,000 Lb
FAW14.3 14,300 Lb
FAW16 16,000 Lb
FA(W)18 18,000 Lb
FA(W)20 20,000 Lb
FA23 23,000 Lb

Pivot Centers
The dimension between the right- and left-hand
pivot centers depends on the design of the
specific axle. A listing of the various front axles
and pivot center dimensions is located in
“FRONT AXLE SPECIFICATIONS” on page 109.

Steering Systems
Power steering is used on all MACK chassis. The Figure 1 — Single Steering Gear with Two-Line Pump
systems used are TRW/TAS or Sheppard integral
power steering gears. The manufacturer’s name 1. Steering Gear 5. Power Steering
is cast into the main housing of the steering gear. 2. Pressure Port Reservoir
3. Power Steering Pump 6. Reservoir Feed Port
To find the specific steering gear model, refer to 4. Suction Port 7. Reservoir Return Port
the chassis build record which is supplied with
each new MACK vehicle. The markings on the
outside of steering gear housings should not be
relied upon to determine the gear model. This is
because the same housing can be used for more
than one model steering gear.

Page 10
 VISUAL IDENTIFICATION
Chassis may also be equipped with two steering
2

gears; a master gear and a slave gear. The slave

gear assembly differs from the master gear in that
it does not have an input shaft. Like the
single-gear systems, the power steering pumps
can be either two-line or three-line pumps.
Figure 3, Figure 4 and Figure 5 show the different
two- and three-line systems for the various
steering gear arrangements used on MACK
chassis.
3

Figure 2 — Single Steering Gear with Three-Line Pump

1. Steering Gear 6. Power Steering

2. Pressure Port Reservoir
3. Power Steering Pump 7. Reservoir Feed Port
4. Suction Port 8. Reservoir Return Port
5. Bypass Line

Figure 3 — Dual-Gear System (TRW Steering Gears)

with Two-Line Pump

1. Master Steering Gear 6. Power Steering

2. Slave Gear Reservoir
3. Pressure Port 7. Reservoir Return Port
4. Power Steering Pump 8. Reservoir Feed Port
5. Suction Port

Page 11
 VISUAL IDENTIFICATION
4 5

Figure 4 — Dual-Gear System (Sheppard Steering Figure 5 — Dual-Gear System (TRW Steering Gears)
Gears) with Two-Line Pump with Three-Line Pump

1. Master Steering Gear 6. Power Steering 1. Slave Gear 6. Power Steering

2. Slave Gear Reservoir 2. Pressure Port Reservoir
3. Suction Port 7. Reservoir Return Port 3. Power Steering Pump 7. Reservoir Feed Port
4. Power Steering Pump 8. Reservoir Feed Port 4. Bypass Line 8. Reservoir Return Port
5. Pressure Port 5. Suction Port 9. Steering Gear

Page 12
 VISUAL IDENTIFICATION
Some models (typically CV and LE) may utilize a
6

booster cylinder to provide additional steering

assist. Figure 7 and Figure 8 show the schematic
diagrams for systems that utilize a booster
cylinder.
7

Figure 6 — Dual-Gear System (Sheppard Steering

Gears) with Three-Line Pump

1. Slave Gear Fluid Return 9. Steering Gear Pressure

2. Slave Gear Port
3. Pressure Port 10. Steering Gear-to-Slave
4. Suction Port Pressure Port Figure 7 — Steering System (TRW Steering Gear) with
5. Power Steering 11. Steering Gear Booster Cylinder and Two-Line Pump
Reservoir 12. Steering Gear Return to
6. Reservoir Feed Port Slave Gear
1. Steering Gear 6. Power Steering
7. Reservoir Return Port 13. Upper Steering Gear to
2. Booster Cylinder Reservoir
8. Bypass Line Lower Slave Gear
3. Power Steering Pump 7. Reservoir Feed Port
4. Suction Port 8. Reservoir Return Port
5. Pressure Port

The difference between the Sheppard and the

TRW dual-gear systems is that on the TRW
system, the return line from the master gear goes
directly to the reservoir.

Page 13
 VISUAL IDENTIFICATION
8

Figure 8 — Steering System (Sheppard Steering Gear)

with Booster Cylinder and Two-Line Pump

1. Steering Gear 6. Power Steering

2. Booster Cylinder Reservoir
3. Power Steering Pump 7. Reservoir Feed Port
4. Suction Port 8. Reservoir Return Port
5. Pressure Port

Page 14
DESCRIPTION AND OPERATION

DESCRIPTION AND OPERATION

Page 15
 DESCRIPTION AND OPERATION
FRONT AXLE AND STEERING connected to the right-hand knuckle. The gear
and power assist slave gear are interconnected
INTRODUCTION hydraulically to provide steering assist.
Front axles used on MACK on-highway and On all axles, the steering knuckles are connected
on-off highway trucks and tractors are a by the cross steering levers and cross steering
drop-forged, heat-treated l-beam with tube to maintain alignment.
reverse-Elliott construction.
On 12,000 through 20,000 lb. front axle
Steering is accomplished by mounting a steering assemblies, the steering kunckles use lower
knuckle on the front axle with a steering knuckle bushings and upper needle bearings to provide a
(king) pin so that each steering knuckle is free to bearing surface for the kingpin. A ball
pivot. Steering input to the steering knuckle (and bearing-type thrust bearing is installed in the
subsequently the front wheels) is achieved lower end of the knuckle assembly to support the
through a drag link that is attached between the weight of the vehicle. On 23,000 lb. axle
steering gear lever (pitman arm) and the steering assemblies, the steering knuckles use upper and
lever that is rigidly mounted to the steering lower bushings to provide a bearing surface for
knuckle. the kingpin. A roller bearing-type thrust bearing is
used at the top of the knuckle assembly to
While most vehicles have the steering lever support the weight of the vehicle. Ball- and
attached to the left knuckle, some vehicles are roller-type thrust bearings provide smooth
built to provide for right-hand steering. In this steering and extended service life. Seals are
case, the linkage and steering lever are mounted used to exclude dirt and retain lubrication inside
on the right-hand knuckle. In special cases, the kunckle assembly.
vehicles are provided with steering levers on both
the right- and left-hand steering knuckles. On The front axles are positioned on the vehicle by
these vehicles, the steering linkage from the the springs that are attached to the frame with
steering gear is connected to the left-hand support brackets.
steering knuckle with a power assist slave gear 9

Figure 9 — Front Axle Arrangement

Page 16
 DESCRIPTION AND OPERATION
Stable steering and normal tire life depend upon The technician performing front axle service
maintaining balanced forces in the front end and should have sufficient knowledge of the basic
steering system. To prevent undesirable effects factors that affect the steering system, to allow
from the various forces acting upon the front end, logical system diagnosis and correction of
it is essential that wheel and tire assemblies be trouble.
properly aligned and balanced. Additionally, all
components of the front axle, suspension and All equipment and instruments used for checking
steering system must be maintained in good or repairing the vehicle must be inspected and
mechanical condition and proper adjustment. adjusted at regular intervals to ensure accuracy.
Inaccurate and unsatisfactory work results when
The information covered in this manual deals with even these instruments are carelessly maintained
front axle and steering specifications, or handled.
maintenance, troubleshooting, repair instructions,
adjustments (which is contained within the repair
instructions section) and special tools.

It must be noted that the steering characteristics

of the vehicle are also dependent upon rear
wheel geometry and frame alignment, besides
wheels and tires. For additional information, refer
to the MACK Master Manuals that cover these
items. All information about vehicle alignment can
be found in Frame, Axle and Suspension Service
and Total Vehicle Alignment, 14-103. Other
pertinent information is detailed in Wheels, Rims
and Tires, 15-101, and Wheel Bearings Service
Manual, 15-701. Current alignment specifications
can be found in the Maintenance and Lubrication
Manual, TS494.

Page 17
 DESCRIPTION AND OPERATION
GLOSSARY Drag Link — This is the mechanical link between
the steering lever and the steering gear lever
The following terms and definitions are used (pitman arm).
periodically throughout this manual, and are
presented here for clarification. Knuckle Pins (Kingpins) — These pins (one on
each side) are used to attach the steering
knuckles to the axle center.
Steering Components
Pivot Center — This is the theoretical point on
Ball Socket (Tie Rod) Assembly — This the knuckle pin axis where it is intersected by the
assembly is installed on each end of the cross axis of the steering knuckle spindle.
steering tube. The ball sockets (tie rods) are
attached to the cross steering levers on the Steering Gear Lever (Pitman Arm) — This lever
steering knuckles. is attached to the steering gear sector shaft and
is connected to the drag link. A timing mark is
Cross Steering Lever — These two arms are scribed on the lever and must be aligned with a
attached to the right- and left-hand steering similar mark on the steering gear sector shaft.
knuckles, and are linked together by the cross
steering tube.

Cross Steering Tube Assembly — This tube

connects the two cross steering levers and
includes the two cross steering socket
10
assemblies. These socket assemblies are
screwed into the cross steering tube ends, which
allow the steering tube to be adjusted for length.

Figure 10 — Steering Components Exploded View

Page 18
 DESCRIPTION AND OPERATION
Steering Gear Sector Shaft — This is the output Road Shock — A kick felt in the steering wheel
shaft of the steering gear to which the steering as the front wheels travel on uneven roads. It is
gear lever (pitman arm) is attached. not noticeable on smooth roads.

Steering Knuckle — This is the movable portion Leading — The tendency of the vehicle to pull in
of the axle that pivots on the knuckle pins the same direction at all times.
(kingpins).
Shimmy — Steer axle shimmy is described as
Steering Knuckle Spindle — This is the part of prolonged steering wheel vibration which occurs
the steering knuckle that the wheel and tire spontaneously at certain vehicle speeds or in
assembly, through the hub and bearings, rotates response to striking a bump. Changing vehicle
around. speed may cause shimmy to stop. Shimmy may
be present on smooth or rough roads.
Steering Lever — This lever is attached to the
steering knuckle and is used to transmit force Tramp — A rhythmic and alternate bouncing of
from the drag link to the steering knuckle, in order the front wheels. Usually noticeable at higher
to turn the wheels. speeds.

Wandering — Straying indiscriminately from side

Troubleshooting Terms to side. Can occur at both low and high speeds.

Chatter — Rapid, intermittent noise or vibration. Wheel Fight — A continuous jerking of the
steering wheel in either direction on rough roads
Diving or Darting — Tendency of the vehicle to at all speeds. Not violent, but extremely annoying
suddenly dive or dart from the direction of travel; and tiring to the driver.
particularly when a tire runs over a hole or
obstruction.

Resonant Ride — This condition is similar to

shimmy in that it occurs spontaneously at certain
vehicle speeds or in response to striking a bump.
Changing vehicle speed may cause resonant ride
to stop. Resonant ride, like shimmy, may be
present on smooth or rough roads. However, this
vibration is felt through the cab or seat instead of
the steering wheel.

Page 19
 NOTES

Page 20
TROUBLESHOOTING

TROUBLESHOOTING

Page 21
 TROUBLESHOOTING
FRONT AXLE AND STEERING Look for abnormal looseness or tightness in the
steering linkage, ball sockets and kingpins, and
TROUBLESHOOTING then have the front end alignment checked.

Preliminary Checks A service replacement hose or fluid line may be

misrouted or may be too small in diameter, or it
may be restricted in some way. Reroute any hose
When a customer comes to you with a problem that is kinked or sharply bent. Replace any hoses
related to the vehicle steering, you can save a lot that are not the same as original equipment.
of time and work if you first verify the problem.
Make sure you are both talking the same Continue by checking the power steering
language about the same problem. If the reservoir to make sure that the fluid is at the
customer says that the truck is “hard to steer,” correct level.
find out exactly what “hard to steer” means. Is it
hard steering into a right- or left-hand turn? Is it These are just some of the checks you should
difficult only when turning the steering wheel make before you turn to the steering gear or
while the truck is sitting still? Is the power pump.
steering intermittent, or is there no power assist
at all? Refer to the following troubleshooting charts that
explain what to diagnose for a particular steering
If at all possible, and if it is safe to do so, test problem. Match the trouble symptom against the
drive the truck. If you’re not familiar with the chart and follow the recommended
vehicle, let the customer drive it while you ride troubleshooting sequence. Doing so will save you
along. Hold the steering wheel while he drives, to time and may prevent unnecessary repairs.
get a feel for the problem. Most driving is done
with the truck hauling a load. Arrange for a load if
one is required to reproduce the steering Hydraulic Tests
problem.
If the checks described thus far all prove
Once you have determined the problem or its satisfactory, it is possible that the cause of the
symptoms, don’t jump right in to tear apart the steering problem can be traced to a lack of
steering gear or pump. In most cases, the pressure or insufficient flow. In this case, you may
steering gear should be the last component have to do more detailed troubleshooting that
checked. There are many other components in involves conducting hydraulic tests. These tests
the steering system that could be causing the are explained in the POWER STEERING
problem. You should check these first. SYSTEM HYDRAULIC TESTS section that
follows the troubleshooting charts.
Begin by checking the steered wheels: Make sure
that the tires are at the correct pressure, that they
are properly sized, and that they are not worn or
damaged.

Page 22
 TROUBLESHOOTING
TROUBLESHOOTING CHARTS
HARD STEERING TROUBLESHOOTING CHART
Condition Possible Cause Correction
Hard Steering Lubrication
Steering gear, axle, steering system and Thoroughly lubricate all points.
chassis.
Fifth Wheel
Damaged or galled. Repair or replace.
Poor lubrication. Lubricate as required.
Improperly positioned. Reposition. (Should be forward of rear axle on
single drive units and forward of tandem axle center
line on tandem drive units. Front axle should be
loaded 80% to 100% of rated capacity.)
Front Tires
Improper air pressure. Inflate to specification.
Unequal size or type. Match tires.
Poor condition or uneven wear. Replace as necessary. (Refer to manufacturer
recommendations for front end corrections.)
Caster
Too high. Set caster to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Steering Gear Adjustment (Causing
Binding)
Worm bearing preload too high. Check and adjust worm bearing preload.
Total mesh preload too high. Check and adjust total mesh preload (center gear as
specified).
Steering Gear Problems The following items require dismantling and repair of
the steering gear. Refer to the manufacturer service
manual.
Roller gear binding in output shaft yoke. Check by backdriving the steering gear by the
pitman arm. Failure to backdrive indicates binding.
Input shaft or bearings worn. When checking worm bearing preload, torque
wrench will give an erratic reading. Correct as
required.
Output shaft binding. Felt as a drag when input shaft is driving output
shaft in the backlash area. Drag also felt by
oscillating output shaft in the backlash area.
Steering Wheel, Shaft, Splines, U-Joints and
Column
Binding. Inspect for proper lubrication, binding and excessive
looseness.
U-joints out of phase, felt every 90 degrees. Rephase. (Align arrows on male and female spline.)
Misphased steering shafts are due to an incorrect
combination of shafts, incorrect assembly of the
shafts on the vehicle or shafts with phasing angles
that are out of specifications.
Steering Gear Mounting
Steering gear mounting causing a bind in gear Check preloads while gear is mounted on frame.
housing. Systematically loosen fasteners to detect uneven
mounting surface.

Page 23
 TROUBLESHOOTING
Condition Possible Cause Correction
Hard Steering Drag Link Ends
(continued) Binding. If horizontal type, check ball for flat spot. If vertical
type, rotate stud to detect for binding.
Axle U-Bolts
Loose axle shifts on front springs. Check spring center tie bolt to make sure it enters
axle. Torque U-bolts to specification.
Wheel Lug Nuts Loose Torque to specification.
Loose Ball Socket (Tie Rod) Joints, Cross Replace as required. Torque to specification.
Steering Lever, Steering Lever
Vehicle Loaded Unevenly Redistribute load.
Excessive Front Wheel Brake Drag Adjust brakes.
Power Steering Components
Insufficient pump pressure. Check pump. Replace as necessary.
Defective pressure relief valve. Replace as necessary.
Low fluid level. Fill power steering reservoir to correct level with the
specified fluid.
Control valve sticking. Repair or replace as necessary.
Defective booster cylinder or slave gear. Repair or replace as necessary.
Incorrect installation of reservoir. Check positioning of reservoir.
Front Axle
Wheel bearings out of adjustment or worn. Adjust or replace as necessary.
Kingpin or thrust bearing loose, binding or Repair or replace as necessary.
seized.
Insufficient clearance between axle beam and Adjust as necessary.
steering knuckle (adjustable tapered kingpins
only).
Bent. Replace axle.
Toe adjustment improper. Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
specifications.)

Page 24
 TROUBLESHOOTING
DARTING/OVERSTEERING TROUBLESHOOTING CHART
Condition Possible Cause Correction
Darting/ Lubrication
Oversteering
Steering gear, axle, steering system and Thoroughly lubricate all points.
chassis.
Steering Gear Mounting
Loose at frame or pitman arm, loose at output Torque fasteners to specification.
shaft.
Steering gear causing a bind in gear housing. Check preloads while gear is mounted on frame.
Systematically loosen fasteners to detect uneven
mounting surface.
Drag Link Ends
Binding or loose. If horizontal type, check ball for flat spot. If vertical
type, rotate stud to detect for binding or looseness.
Drag Link Length
Too long or too short causing steering gear to Center steering gear, set front wheels straight
operate off center. ahead, adjust drag link length.
Note: Non-adjustable drag links are used on
certain MACK chassis.
Toe Adjustment Improper Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
alignment specifications.)
Axle U-Bolts
Loose axle shifts on front springs. Check spring center tie bolt to make sure it enters
axle. Torque U-bolts to specification.
Suspension (Front and Rear)
Weak or broken springs, or damaged air bags. Replace springs or replace air bags.
Worn shackle/spring pins and bushings. Replace as necessary.
Wheel Lug Nuts Loose Torque to specification.
Frame
Twisted, sprung diamound-shaped. Have frame checked by specialist.
Loose Ball Socket (Tie Rod) Joints, Cross Replace as required. Torque to specification.
Steering Lever, Steering Lever
Engine Mounts Broken or Loose Repair or replace as necessary.
Vehicle Loaded Unevenly Redistribute load.
Tandem
Out of alignment. Check and align to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Worn wheel bearings. Replace and adjust as necessary.
Excessive Front Wheel Brake Drag Adjust brakes.

Page 25
 TROUBLESHOOTING
Condition Possible Cause Correction
Darting/ Front Axle
Oversteering
(continued) Wheel bearings out of adjustment or worn. Adjust or replace as necessary.
Kingpin or thrust bearing loose, binding or Repair or replace as necessary.
seized.
Insufficient clearance between axle beam and Adjust as necessary.
steering knuckle (adjustable tapered kingpins
only).
Bent. Replace axle.
Toe adjustment improper. Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
alignment specifications.)

Page 26
 TROUBLESHOOTING
WANDERING TROUBLESHOOTING CHART
Condition Possible Cause Correction
Wandering Fifth Wheel
Damaged or galled. Repair or replace as necessary.
Poor lubrication. Lubricate as necessary.
Improperly positioned. Reposition. (Should be forward of rear axle on
single drive units and forward of tandem axle center
line on tandem drive units. Front axle should be
loaded 80% to 100% of rated capacity.)
Front Tires
Improper air pressure. Inflate to specification.
Unequal size or type. Match tires.
Poor condition or uneven wear. Replace as necessary. (Refer to manufacturer
recommendations for front end corrections.)
Caster
Too low. Set caster to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Steering Gear Adjustments
Worm bearing preload too low permitting end Check and adjust worm bearing preload.
play.
Total mesh preload too low resulting in gear Check and adjust total mesh preload and center the
backlash. steering gear as specified.
Steering Gear Problems The following items require dismantling and repair of
the steering gear. Refer to the manufacturer service
manual.
Roller gear binding in output shaft yoke. Check by backdriving the steering gear by the
pitman arm. Failure to backdrive indicates binding.
Input shaft or bearings worn. When checking worm bearing preload, torque
wrench will give an erratic reading. Correct as
required.
Output shaft binding. Felt as a drag when input shaft is driving output
shaft in the backlash area. Drag also felt by
oscillating output shaft in the backlash area.
Steering Wheel, Shaft, Splines, U-Joints and
Column
Loose. Check for proper lubrication, binding and excessive
looseness. Replace as specified by the
manufacturer.
U-joints worn, felt every 180 degrees. Replace as necessary.
Steering Gear Mounting
Loose at frame or pitman arm, loose at output Torque fasteners to specification.
shaft.
Drag Link Ends
Loose. If horizontal type, check ball for flat spot. If vertical
type, rotate stud to detect for binding or looseness.
Drag Link Length
Too long or too short causing steering gear to Center steering gear, set front wheels straight
operate off center. ahead, adjust drag link length.
Note: Non-adjustable drag links are used on certain
MACK chassis.

Page 27
 TROUBLESHOOTING
Condition Possible Cause Correction
Wandering Suspension (Front and Rear)
(continued)
Weak or broken springs or damaged air bags. Replace springs or replace air bags.
Worn shackle/spring pins and bushings. Replace as necessary.
Wheel Lug Nuts Loose Torque to specification.
Loose Ball Socket (Tie Rod) Joints, Cross Replace as required. Torque to specification.
Steering Lever, Steering Lever
Engine Mounts Broken or Loose Repair or replace as necessary.
Vehicle Loaded Unevenly Redistribute load.
Excessive Front Wheel Brake Drag Adjust brakes.
Frame
Twisted, sprung, diamond-shaped. Have frame checked by specialist.
Front Axle
Wheel bearings out of adjustment or worn. Adjust or replace as necessary.
Kingpin or thrust bearing loose, binding or Repair or replace as necessary.
seized.
Insufficient clearance between axle beam and Adjust as necessary.
steering knuckle (adjustable tapered kingpins
only).
Bent. Replace axle.
Toe adjustment improper. Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
alignment specifications.)

Page 28
 TROUBLESHOOTING
TOO MUCH FREE PLAY TROUBLESHOOTING CHART
Condition Possible Cause Correction
Too Much Free Fifth Wheel
Play
Damaged or galled. Repair or replace.
Poor lubrication. Lubricate as required.
Improperly positioned. Reposition. (Should be forward of rear axle on
single drive units and forward of tandem axle center
line on tandem drive units. Front axle should be
loaded 80% to 100% of rated capacity.)
Front Tires
Improper air pressure. Inflate to specification.
Unequal size or type. Match tires.
Poor condition or uneven wear. Replace as necessary. (Refer to manufacturer
recommendations for front end corrections.)
Caster
Too low or too high. Set caster to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Steering Gear Adjustment (Causing
Binding)
Worm bearing preload too low. Check and adjust worm bearing preload.
Total mesh preload too low. Check and adjust total mesh preload. (Center gear
as specified.)
Steering Gear Problems The following items require dismantling and repair of
the steering gear. Refer to the manufacturer service
manual.
Input shaft or bearings worn. When checking worm bearing preload, torque
wrench will give an erratic reading. Correct as
required.
Steering Wheel, Shaft, Splines, U-Joints and
Column
Loose. Inspect for proper lubrication, binding and excessive
looseness. Replace as specified by the
manufacturer.
U-joints worn, felt every 180 degrees. Replace.
Steering Gear Mounting
Loose at frame or pitman arm, loose at output Torque fasteners to specification.
shaft.
Drag Link Ends
Loose. If horizontal type, check ball for flat spot. If vertical
type, rotate stud to detect for binding or looseness.
Drag Link Length
Too long or too short causing steering gear to Center steering gear, set front wheels straight
operate off center. ahead and adjust drag link length.
Note: Non-adjustable drag links are used on certain
MACK chassis.
Wheel Lug Nuts Loose Torque to specification.
Loose Ball Socket (Tie Rod) Joints, Cross Replace as required. Torque to specification.
Steering Lever, Steering Lever
Vehicle Loaded Unevenly Redistribute load.

Page 29
 TROUBLESHOOTING
Condition Possible Cause Correction
Too Much Free Front Axle
Play (continued)
Wheel bearings out of adjustment or worn. Adjust or replace as necessary.
Kingpin or thrust bearing loose, binding or Repair or replace as necessary.
seized.
Insufficient clearance between axle beam and Adjust as necessary.
steering knuckle (adjustable tapered kingpins
only).
Bent. Replace axle.
Toe adjustment improper. Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
alignment specifications.)

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 TROUBLESHOOTING
LEADING (PULL) TROUBLESHOOTING CHART
Condition Possible Cause Correction
Leading (Pull) Fifth Wheel
Damaged or galled. Repair or replace.
Poor lubrication. Lubricate as required.
Improperly positioned. Reposition. (Should be forward of rear axle on
single drive units and forward of tandem axle center
line on tandem drive units. Front axle should be
loaded 80% to 100% of rated capacity.)
Front Tires
Improper air pressure. Inflate to specification.
Unequal size or type. Match tires.
Poor condition or uneven wear. Replace as necessary. (Refer to manufacturer
recommendations for front end corrections.)
Caster
Unequal. (More than 1/2 degree difference Check for bent or twisted axle. Replace as
between right and left sides.) necessary. Set caster to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Toe Adjustment Improper Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
alignment specifications.)
Axle U-Bolts
Loose axle shifts on front springs. Check spring center tie bolt to make sure it enters
axle. Torque U-bolts to specification.
Suspension (Front and Rear)
Weak or broken springs, or damaged air bags. Replace springs or replace air bags.
Worn shackle/spring pins and bushings. Replace as necessary.
Wheel Lug Nuts Loose Torque to specification.
Loose Ball Socket (Tie Rod) Joints, Cross Replace as required. Torque to specification.
Steering Lever, Steering Lever
Engine Mounts Broken or Loose Repair or replace as necessary.
Vehicle Loaded Unevenly Redistribute load.
Tandem
Out of alignment. Set alignment to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Worn wheel bearings. Replace and adjust as necessary.
Excessive Front Wheel Brake Drag Adjust brakes.
Frame
Twisted, sprung, diamond-shaped. Have frame checked by specialist.

Page 31
 TROUBLESHOOTING
Condition Possible Cause Correction
Leading (Pull) Front Axle
(contined)
Wheel bearings out of adjustment or worn. Adjust or replace as necessary.
Kingpin or thrust bearing loose, binding or Repair or replace as necessary.
seized.
Insufficient clearance between axle beam and Adjust as necessary.
steering knuckle (adjustable tapered kingpins
only).
Bent. Replace axle.
Toe adjustment improper. Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
alignment specifications.)

Page 32
 TROUBLESHOOTING
NO WHEEL RECOVERY TROUBLESHOOTING CHART
Condition Possible Cause Correction
No Wheel Lubrication
Recovery
Steering gear. Inspect lubricant for metal shavings, water or
excessive thickness. Fill or replace with proper
lubricant.
Axle, steering system and chassis. Thoroughly lubricate all points.
Fifth Wheel
Damaged or galled. Repair or replace.
Poor lubrication. Lubricate as required.
Improperly positioned. Reposition. (Should be forward of rear axle on
single drive units and forward of tandem axle center
line on tandem drive units. Front axle should be
loaded 80% to 100% of rated capacity.)
Front Tires
Improper air pressure. Inflate to specification.
Unequal size or type. Match tires.
Poor condition or uneven wear. Replace as necessary. (Refer to manufacturer
recommendations for front end corrections.)
Caster
Too low. Set caster to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Steering Gear Adjustment (Causing
Binding)
Worm bearing preload too high. Check and adjust worm bearing preload.
Total mesh preload too high. Check and adjust total mesh preload. (Center gear
as specified.)
Steering Gear Problems The following items require dismantling and repair of
the steering gear. Refer to the manufacturer service
manual.
Roller gear binding in output shaft yoke. Check by backdriving the steering gear by the
pitman arm. Failure to backdrive indicates binding.
Input shaft or bearings worn. When checking worm bearing preload, torque
wrench will give an erratic reading. Correct as
required.
Output shaft binding. Felt as a drag when input shaft is driving output
shaft in the backlash area. Drag also felt by
oscillating output shaft in the backlash area.
Bent worm gear. Felt as an erratic torque reading every 360 degrees
through mesh.
Steering gear bottoming. Turn steering wheel lock-to-lock and check for
bottoming. Adjust wheel stops to limit turns before
steering gear bottoms.
Control valve sticking and not centering. Repair or replace as necessary.
Steering Wheel, Shaft, Splines, U-Joints and
Column
Binding. Inspect for proper lubrication, binding and excessive
looseness.

Page 33
 TROUBLESHOOTING
Condition Possible Cause Correction
No Wheel Steering Gear Mounting
Recovery
(continued) Steering gear mounting causing a bind in gear Check preloads while gear is mounted on frame.
housing. Systematically loosen fasteners to detect uneven
mounting surface.
Drag Link Ends
Binding. If horizontal type, check ball for flat spot. If vertical
type, rotate stud to detect for binding.
Wheel Lug Nuts Loose Tighten to specification.
Excessive Front Wheel Brake Drag Adjust brakes.
Front Axle
Wheel bearings out of adjustment or worn. Adjust or replace as necessary.
Kingpin or thrust bearing loose, binding or Repair or replace as necessary.
seized.
Insufficient clearance between axle beam and Adjust as necessary.
steering knuckle (adjustable tapered kingpins
only).
Bent. Replace axle.
Toe adjustment improper. Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
alignment specifications.)

SHIMMY AT HIGH SPEED TROUBLESHOOTING CHART

Condition Possible Cause Correction
Shimmy at High Front Wheels and Tires
Speed
Out of balance. Have balanced by specialist.
Shock Absorbers Worn Inspect and replace as necessary.
Tandem
Out of alignment. Check and set to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Worn wheel bearings. Replace and adjust as necessary.
Frame
Twisted, sprung, diamond-shaped. Have frame checked by specialist.

Page 34
 TROUBLESHOOTING
SHIMMY AT LOW SPEED TROUBLESHOOTING CHART
Condition Possible Cause Correction
Shimmy at Low Front Tires
Speed
Improper air pressure. Inflate to specification.
Unequal size or type. Match tires.
Poor condition or uneven wear. Replace as necessary. (Refer to manufacturer
recommendations for front end corrections.)
Caster
Too high. Set caster to specification. (Refer to the
Maintenance and Lubrication Manual, TS494, for
most current alignment specifications.)
Steering Gear Adjustment
Worm bearing preload too low, permitting end Check and adjust worm bearing preload.
play.
Total mesh preload too low, resulting in gear Check and adjust total mesh preload (center gear as
backlash. specified).
Air in hydraulic system. Bleed system and check pump seal.
Steering Gear Problems The following items require dismantling and repair of
the steering gear. Refer to the manufacturer service
manual.
Input shaft or bearings worn. When checking worm bearing preload, torque
wrench will give an erratic reading. Correct as
required.
Defective control valve. Replace control valve as necessary.
Steering Wheel, Shaft, Splines, U-Joints and
Column
Loose. Inspect for proper lubrication, binding, and
excessive looseness. Replace as specified by the
manufacturer.
U-joints worn, felt every 180 degrees. Replace.
Steering Gear Mounting
Loose at frame or pitman arm, loose at output Torque fasteners to specification.
shaft.
Drag Link Ends
Loose. If horizontal type, check ball for flat spot. If vertical
type, rotate stud to detect for binding or looseness.
Drag Link Length
Too long or too short, causing steering gear to Center steering gear, set front wheels straight
operate off center. ahead and adjust drag link length.
Note: Non-adjustable drag links are used on certain
MACK chassis.
Axle U-Bolts
Loose axle shifts on front springs Check spring center tie bolt to make sure it enters
axle. Torque U-bolts to specification.
Wheel Lug Nuts Loose Torque to specification
Loose Ball Socket (Tie Rod) Joints, Cross Replace as required. Torque to specification.
Steering Lever, Steering Lever
Tandem
Worn wheel bearings. Replace and adjust as required.

Page 35
 TROUBLESHOOTING
Condition Possible Cause Correction
Shimmy at Low Front Axle
Speed (continued)
Wheel bearings out of adjustment or worn. Adjust or replace as necessary.
Kingpin or thrust bearing loose, binding or Repair or replace as necessary.
seized.
Insufficient clearance between axle beam and Adjust as necessary.
steering knuckle (adjustable tapered kingpins
only).
Bent. Replace axle.
Toe adjustment improper. Set toe to specification. (Refer to the Maintenance
and Lubrication Manual, TS494, for most current
alignment specifications.)

KNOTTY FEEL TROUBLESHOOTING CHART

Condition Possible Cause Correction
Knotty Feel Lubrication
Steering gear. Inspect lubricant for metal shavings, water or
excessive thickness. Fill or replace with proper
lubricant.
Axle, steering system and chassis. Thoroughly lubricate all points.
Steering Gear Problems The following items require dismantling and repair of
the steering gear. Refer to the manufacturer service
manual.
Input shaft or bearings worn. When checking worm bearing preload, torque
wrench will give an erratic reading. Correct as
required.
Bent worm gear. Felt as an erratic torque reading every 360 degrees
through mesh.
Steering Wheel, Shaft, Splines, U-Joints and
Column
Binding. Inspect for proper lubrication, binding and excessive
looseness.
U-joints worn, felt every 180 degrees. Replace as necessary.
U-joints out of phase, felt every 90 degrees. Rephase. (Align arrows on male and female
splines.)
Steering Gear Mounting
Loose at frame or pitman arm, loose at output Torque fasteners to specification.
shaft.
Steering gear mounting causing a bind in gear Check preloads while gear is mounted on frame.
housing. Systematically loosen fasteners to detect uneven
mounting surface.
Drag Link Ends
Binding. If horizontal type, check ball for flat spot. If vertical
type, rotate stud to detect for binding.

Page 36
 TROUBLESHOOTING
MISCELLANEOUS CONDITIONS TROUBLESHOOTING CHART
Condition Possible Cause Correction
Direction of Lines connected incorrectly. Check for proper line connections.
Steering Reversed
Incorrect steering gear used (if just replaced). Check for use of proper steering gear.
Lack of Assist Inadequate output from pump, particularly at Check and replace pump as necessary.
When Turning idle speed (flow).
Steering Wheel
Rapidly
Intermittent Power Fluid level low. Fill power steering reservoir with specified fluid.
Steering
Air in system. Bleed system and check pump seal.
Relief valve sticking. Repair or replace valve assembly as necessary.
Noisy Pump Pump inlet restricted. Investigate to relieve restriction.
Fluid level low. Fill power steering reservoir with specified fluid.
Air in system. Bleed system and check pump seal.
Relief valve sticking. Repair or replace valve assembly as necessary.
Pump worn. Replace pump.
Fluid Foaming Fluid level low. Fill power steering reservoir with specified fluid.
Air in system. Bleed system and check pump seal.
Sucking air. Check pump seals and replace as necessary.
Power Steering in Control valve malfunction. Adjust or replace control valve assembly as
One Direction Only necessary.

Page 37
 TROUBLESHOOTING
POWER STEERING SYSTEM If a special hydraulic circuit tester is not available,
the steering system can be checked with a
HYDRAULIC TESTS standard pressure gauge of at least 3,000 psi
[411] (20 685 kPa) capacity, a regulator valve to permit
loading the system and a thermometer.
Once the possibility of external mechanical
problems in the steering linkage and components Testing of the steering system should be done in
has been eliminated, the hydraulic system should the sequence specified, unless a particular test
be checked. does not apply. If this is the case, skip the
unneeded test and proceed to the next test. Refer
The recommended method for troubleshooting to the proper vendor information for specific
the power steering system is by using special steering gear or pump information not covered in
hydraulic system testers such as Kent-Moore this section.
Power Steering Analyzer J 26487-C, or
equivalent. These testers or analyzers measure When troubleshooting a power steering system,
pressure, flow rate in gallons per minute (gpm), always fill out Form PV771-500-05 “Power
fluid temperature, and incorporate a restriction Steering Troubleshooting Report.” A copy of this
(load) valve that permits loading the system to form must be attached to any replaced steering
determine pressure relief. Basically, the test component, and the form must be retained at the
procedures consist of checking the system in a repair facility for subsequent review by a MACK
loaded and an unloaded condition, and then District Service Representative.
comparing flow and pressure while isolating each
component. Fill out this form when troubleshooting power
steering systems.

Page 38
 TROUBLESHOOTING
11

Figure 11 — Power Steering Troubleshooting Report

Page 39
 TROUBLESHOOTING
Power Steering Pump Model Codes VICKERS
On Vickers pumps, the model code is located on
MACK chassis use either Vickers, LUK, TRW or the pump nameplate. It consists of several
ZF power steering pumps. On Vickers and TRW groups of letters and/or numbers as shown in
pumps, maximum flow rate of the pump can be Figure 12 and Figure 13. Asterisks are used in
determined by referring to the model code the following figures to indicate characters in the
stamped on the pump identification plate. On code that do not apply. Only the items that apply
LUK and ZF pumps, the pressure relief valve to flow rate and relief valve settings are shown.
setting is stamped on the pump ID plate. Be guided by number groups rather than number
of characters, since the number of characters in a
group can vary. Breakdowns are given for V20
series and V10 series pumps.
12

Figure 12 — Model Code Break-Down for Vickers V10 and V20 Series Pumps

Page 40
 TROUBLESHOOTING
TRW Pumps identify different characteristics of the pump. The
third group of numbers in the model code
On TRW pumps, the model code which is identifies the pump flow, and the fourth group of
stamped on the identification plate, consists of numbers identifies the relief valve setting (refer to
several groups of letters and numbers that Figure 13).
13

Figure 13 — TRW Power Steering Pump Model Code

LUK
On LUK pumps, the pump pressure relief setting
(in bars) is stamped on the identification plate.
LUK pumps are available with the following three
pressure relief settings:
앫 140 bar = 2,031 psi (14 187 kPa)
앫 150 bar = 2,176 psi (15 004 kPa)
앫 163 bar = 2,364 psi (16 300 kPa)

The LUK pump is also available with a maximum

flow rating of either 5 gpm or 4 gpm. The MACK
part number, also found on the pump
identification plate, can be used to determine the
maximum flow rating. Pumps that have a part
number ending with M, M2, M3, M4 or M6 are
rated at 5 gpm flow. Pumps that have a part
number ending with M5 are rated at 4 gpm flow.

Page 41
 TROUBLESHOOTING
ZF Pumps
14

The power steering pump used on MACK MP

engines is a tandem pump where the power
steering pump and the fuel supply pump are
bolted together and driven by the same drive
gear. The pressure relief setting is stamped on
the identification plate. The pumps are available
with the following pressure relief settings:
앫 2002 psi (138 bar)
앫 2176 psi (150 bar)
앫 2321 psi (160 bar)
앫 2611 psi (180 bar)
앫 2756 psi (190 bar)
앫 2901 psi (200 bar)

The ZF pump is available with the following

maximum flow ratings:
앫 3.7 gpm (14 lpm)
앫 4.2 gpm (16 lpm)
앫 5.3 gpm (20 lpm)
앫 5.6 gpm (21 lpm)
앫 6.3 gpm (24 lpm)
Figure 14 — ZF Tandem (Power Steering/Fuel Supply)
앫 6.6 gpm (25 lpm) Pump

1. Power Steering Pump 3. Pump ID Plate

2. Fuel Supply Pump

Page 42
 TROUBLESHOOTING
Steering Gear and Pump Flow power steering pump. The following table lists the
required pump flow and maximum operating
Requirements pressures for the specific steering gears used on
MACK chassis.
Power steering gears are designed to operate at
a specific maximum pressure, and require a
minimum and maximum fluid flow range from the

STEERING GEAR FLOW REQUIREMENTS

Minimum Flow Flow Range Maximum Pressure
Manufacturer Model GPM (LPM) GPM (LPM) PSI (BAR)
Sheppard Single Gear M90P 2.5 (9.5) 2.5–6.0 (9.5–22.7) 2,175 (150)
M100P 3.0 (11.4) 3.0–6.0 (11.4–22.7) 2,175 (150)
M110P 3.5 (13) 3.5–5.0 (13–19) 2,349 (162)
392S 3.3 (12.5) 3.3–5.0 (12.5–18.9) 2,000 (138)
492S 4.3 (16.3) 4.3–6.0 (16.3–22.7) 2,000 (138)
592S 5.7 (21.6) 5.7–7.0 (21.6–26.5) 2,000 (138)
Sheppard Dual Gear M100P/M90 Total 5.5 (20.8) 5.5–6.5 (20.8–24.6) 2,349 (162)
System Flow

M100P (Master) 3.0 (11.4) 3.0–4.5 (11.4–17.0) 2,349 (162)

M90 (Slave) 2.5 (9.5) 2.5–4.5 (9.5–17.0) 2,349 (162)
392S/292S Total 4.9 (18.6) 4.9–7.0 (18.6–26.5) 2,000 (138)
System Flow

393S (Master) 3.3 (12.5) 3.3–5.0 (12.5–18.9) 2,000 (138)

292S (Slave) 1.6 (6.1) 1.6–5.0 (6.4–18.9) 2,000 (138)
TRW/TAS Single Gear M100P/M90 Total 3.0 (11.4) 3.0–8.0 (11.4–30.3) 2,175 (150)
System Flow
TAS85 3.6 (13.6) 3.6–8.0 (13.6–30.3) 2,175 (150)
TRW/TAS Dual Gear TAS65/RCS40 Total 5.2 (19.7) 5.2–8.0 (19.7–30.3) 2,175 (150)
System Flow
TAS65 (Master) 3.0 (11.4) 3.0–8.0 (11.4–30.3) 2,175 (150)
RCS40 (Slave) 2.2 (8.3) 2.2–8.0 (8.3–30.3) 2,175 (150)

The maximum pressures given in the last column

of the chart above are maximum pressure ratings
of the steering gears. For actual steering system
pressures, refer to the pressure relief valve
setting stamped on the pump.

Page 43
 TROUBLESHOOTING
Fluid Foaming Check 2. Insert thermometer J 5421-02, or equivalent,
into the reservoir.
1. Check the level and condition of the fluid in
the power steering reservoir. If required, fill 3. Start the engine. Turn the steering wheel
the reservoir to the proper level using the from stop-to-stop for approximately
specified fluid. Any system with indications 10 minutes to bring the system up to normal
of “scorched” fluid or fluid contaminated with operating temperature. Operating
either water or abrasive must be drained and temperature range should be between
refilled. The filter should also be changed at 160°F (71°C) and 170°F (77°C). The
the same time. temperature must never exceed 235°F
15 (113°C). High temperatures break down the
fluid, and damage seals, hoses, control
valves and relief valves.
4. Check for foaming through the filler hole in
the reservoir. If foaming occurs, check for air
leaks on the inlet (suction) side of the pump.
Make sure that all fittings are tight. Install a
new pump inlet hose, if the hose is leaking.
16

Figure 15 — Checking Reservoir Fluid Level

DO NOT operate the power steering pump at

maximum pressure for more than 10 seconds.
Doing this can overheat the fluid and damage the
pump and/or other steering system components. Figure 16 — Checking for Fluid Foaming

Page 44
 TROUBLESHOOTING
Power Steering Pump Performance
17

Test
Power steering pump performance can be tested
by measuring pump flow and comparing it to the
maximum flow rating of the pump. To perform this
test, the pump is isolated from the steering
system. Do this by disconnecting the pressure
line at the steering gear and reconnecting this
pressure line to a power steering analyzer, such
as Kent-Moore J 26487-C, or equivalent. The
outlet line of the analyzer is inserted into the
power steering reservoir. All power steering fluid
is pumped directly through the analyzer and
returned to the reservoir.
1. Disconnect the power steering pump
pressure line from the steering gear inlet.
Plug the steering gear inlet. Connect one
end of a hose required for testing to the
Figure 17 — Pump Inlet Connection pressure line of the pump and the other end
to the analyzer. Connect another hose from
5. If foaming is still present, stop engine and the analyzer outlet to the reservoir.
18
drain and refill the system with the specified
fluid.
6. If foaming persists, replace the pump shaft
seal.

Figure 18 — Connections for Pump Performance Test

1. Pressure Line to Test 4. Return Line to Reservoir

Hose Connection 5. Power Steering Analyzer
2. Pressure Line from Pump J 26487-C
3. Steering Gear Inlet
Plugged

Page 45
 TROUBLESHOOTING
3. Run the engine at a speed that operates the
19

power steering pump at 1,200 rpm. Refer to

the following table.

PUMP-TO-ENGINE RPM RATIO

Engine
Engine ID Location Ratio Speed
MACK E6 End of Air 1:1 1200
(Early) Compressor
MACK E6 and End of Auxiliary Shaft 1:1 1200
(Later)
MACK E7
MACK E9 Front of Engine (12 1:1 1200
O’Clock Position)
MACK End of Auxiliary Shaft 1.22:1 985
E-Tech™ and (Spline Driven) or
ASET™ Back of Compressor
MACK E5 Left Rear Side of 1.41:1 850
Engine (Gear Driven
Off Crankshaft Idler)
Cummins ISC End of Air 1:1 1200
Figure 19 — Return Line to Reservoir and ISX Compressor (Spline
Driven)
1. Return Line from Power 2. Thermometer J 5421-02 MACK MP7 Lower Left Rear Side 1.74:1 700
Steering Analyzer of Engine (Gear
Driven Off Timing
Gear Idler)
2. Open the load valve on the power steering
analyzer and then, start the engine. 4. Slowly close the analyzer load valve until the
pressure gauge indicates approximately
1,500 psi. This places a load on the pump to
help bring the power steering fluid to
Make sure the analyzer load valve is fully open. operating temperature. Run the pump until
20
the steering system fluid temperature
reaches approximately 160°F–170°F
(71°C–77°C). Do not allow the system fluid
temperature to exceed 235°F (113°C).

Do not place a load on the pump equal to, or

greater than, the operating pressure of the
steering system. Refer to tables on page 43,
Steering Gear and Pump Flow Requirements, for
maximum system pressure.

5. After the power steering fluid temperature

reaches normal operating range, open the
analyzer load valve until the pressure gauge
Figure 20 — Opening Analyzer J 26487-C Load Valve indicates 0 psi.

Page 46
 TROUBLESHOOTING

With the analyzer load valve fully opened, there Do not run the pump at maximum pressure (relief
may be a reading slightly greater than 0 psi due valve open) for longer than 10 seconds. Damage
to back pressure in the system. to the pump can occur. Closing the load valve
causes the pump to operate at relief pressure and
6. Check the operation of the pressure relief the fluid temperature to increase rapidly. Allow
valve in the pump by slowly closing the fluid to cool to between 160°F (71°C) and 170°F
analyzer load valve until the valve opens. (77°C) before you resume with the other tests.
Pressure relief valve opening occurs when
the flow reading on the analyzer drops to 0. 9. Pump flow should be the same, or close to
Flow reading drops to 0 because power the same, from 0 psi up to maximum pump
steering fluid flow is diverted. On chassis pressure (just before relief valve opens). If
equipped with three-line power steering pump flow drops off significantly at higher
pumps, fluid flow is diverted back to the pressures, the pump is worn and should be
reservoir. With two-line pumps, however, rebuilt or replaced in accordance with the
fluid recirculates inside the pump. pump manufacturer specifications.
The pressure relief valve should open at
maximum system pressure. Note the
pressure at which the relief valve opens as
indicated on the analyzer pressure gauge. If the power steering pump has failed, make sure
Open the load valve and repeat this to check and verify correct power steering gear
procedure several times to ensure relief poppet adjustment. If the steering gear relief
consistent relief valve operation. poppet adjustment is incorrect, this could cause
the power steering pump to run at maximum
pressure (relief valve open) when the steering is
at full-left or full-right stops. Without correction to
Do not allow the pump to operate at maximum the relief poppet adjustment, damage to the
pressure (relief valve open) for longer than replacement power steering pump can result.
10 seconds. Damage to the pump can occur.

7. Pump flow should be checked to verify that

the pump is the correct pump for the
steering gear used in the system. With the
power steering pump operating at 1,200 rpm
and the analyzer load valve fully open,
compare the actual pump flow indicated on
the analyzer, to the flow specifications in
tables on page 43, Steering Gear and Pump
Flow Requirements Chart. If the flow rate at
1,200 rpm and 0 psi is not as specified for
the steering gear model found in the table,
check to see if the model of the power
steering pump is correct for the vehicle
application. If the pump is the incorrect
model, replace the pump.
8. To test pump flow, slowly close the analyzer
load valve in 500 psi increments. Note the
flow at each increment, up to the point at
which the pump pressure relief valve opens.

Page 47
 TROUBLESHOOTING
Power Steering Gear Internal
22

Leakage Flow Test

Sheppard and TRW steering gears used on

vocational chassis utilize an internal pressure
relief valve. This valve must be removed and
replaced with a test plug when performing
steering gear internal leakage flow tests. If the
internal pressure relief valve is not removed and
the test plug installed in its place, the valve will
open during the test, resulting in a false indication
of excessive internal leakage. Part numbers for
the test plugs are as follows:
앫 Sheppard steering gears — 8148-3331812K
앫 TRW steering gears — J 37130
On Sheppard steering gears, the pressure relief
valve is located on the side of the steering gear
bearing cap and looks like a 1-1/2″ nut. Figure 22 — TRW Steering Gear Pressure Relief Valve
Location
On TRW steering gears, the pressure relief valve
is located on the inboard side of the rotary valve
1. Steering Gear Pressure Relief Valve
housing.
21
Steering gear internal leakage can be checked by
measuring fluid flow through the gear (use
Kent-Moore power steering analyzer J 26487-C,
or equivalent). This test is performed by placing
blocks between the steering knuckle stop bolts
and the axle. This is done to physically stop the
steering gear before the internal pressure relief
poppets actuate. When the steering wheel is
turned to its maximum position (knuckle stop bolt
contacts block at axle) either left or right,
pressure builds in the system until the pump
pressure relief valve opens. At this point, fluid
flow returning to the reservoir through the
steering gear, indicates leakage inside the gear.
1. Connect the power steering analyzer inlet
line to the discharge (return) side of the
steering gear. Insert the outlet line from the
analyzer into the power steering reservoir.

Figure 21 — Sheppard Steering Gear Pressure Relief Plug any lines or ports that remain open.
Valve Location

1. Steering Gear Pressure Relief Valve

Page 48
 TROUBLESHOOTING
2. If so equipped, remove the pressure relief
24

valve from the steering gear and install a

test plug (part Nos. 8148-3331812K for
Sheppard steering gears, or J 37130 for
TRW steering gears. Tighten only until snug,
do not over-tighten.
23

Figure 24 — Opening Analyzer J 26487-C Load Valve

This test requires that steel blocks be placed

between the axle and the steering knuckle
stop bolts. This is done to prevent the
steering gear internal relief poppets from
actuating when the steering gear is turned
fully in either direction. The blocks must be
secured squarely between the stop bolts and
the axle, and fingers must be kept clear to
Figure 23 — Setup for Checking Internal Gear Leakage prevent serious personal injury. Keep hands
and fingers clear of this area.
1. Inlet Line to Discharge 2. Outlet Line to Reservoir
(Return) Line on Steering 3. Steering Analyzer
Gear J 26487-C 4. Secure a steel block between the axle and
the steering knuckle stop bolt so that the
3. Make sure the analyzer load valve is fully wheels cannot be turned far enough to
open. Start the engine and run at a speed actuate the internal pressure relief poppets.
that operates the power steering pump at
1,200 rpm (refer to table on page 46,
Pump-to-Engine RPM Ratio). The power
steering fluid should be at operating
temperature (160°F–170°F [71°C–77°C])
when performing this test.

Page 49
 TROUBLESHOOTING
Ideally, flow should drop to 0 when the steering
25

gear is fully turned and the pump pressure relief

valve opens. However, hydraulic components by
design, have a certain amount of internal leakage
to provide lubrication. If the flow exceeds the
amount shown in the following table, for the
particular steering gear being tested, internal
leakage is excessive and so the steering gear
must be repaired or replaced. On chassis
equipped with dual steering gears, test overall
system leakage first. If maximum allowable
leakage exceeds the specification listed in the
chart below for a dual gear system, isolate the
main gear from the slave gear by disconnecting
the high pressure lines that run between the two
gears. Disconnect the lines at the master gear,
and then plug the open ports and cap the lines.
Teat leakage through the master gear. If leakage
exceeds the specification listed in the chart for
the individual steering gear, repair or replace the
master gear. If leakage through the master gear
is within specifications, repair or replace the slave
Figure 25 — Securing Steel Block gear. Refer to the manufacturer service manual
for the particular steering gear being serviced.

Maximum Allowable
Steering Gear Leakage GPM (LPM)
Do not allow the power steering pump to operate TRW/TAS (All models) 1.0 (3.8)
at maximum pressure for more than 10 seconds. TRW/TAS Dual Gears 2.0 (7.6)
Damage to the pump can result. (All Models)
Sheppard Model 292 1.5 (5.7)
5. Turn the steering wheel full to the left (until
Sheppard Model 392 1.7 (6.4)
the stop bolt contacts the steel block). Pull
firmly on the steering wheel to ensure that Sheppard Model 492 1.9 (7.2)
the steering gear control (rotary) valve is Sheppard Model 592 2.5 (9.5)
positioned to allow full fluid flow into the Sheppard M110P 1.5 (5.7)
steering gear.
Sheppard M100P 1.5 (5.7)
6. Turn the steering wheel fully to the right
Sheppard M90 1.5 (5.7)
(until the stop bolt contacts the steel block).
Pull firmly on the steering wheel to ensure Sheppard Dual Gears 3.0 (11.4)
M100/M90
the steering gear control (rotary) valve is
positioned to allow full fluid flow into the Sheppard Dual Gears 3.2 (12.1)
steering gear. 392S and 292

7. If so equipped, remove the test plug from the

steering gear and reinstall the pressure relief
valve.

Page 50
 TROUBLESHOOTING
VEHICLE INSPECTIONS AND Inspections and Measurements
MEASUREMENTS FOR Chart
SHIMMY AND RESONANT RIDE
Once the complaint has been properly identified,
use Chart No. 1 to determine the inspections and
Introduction measurements which should be performed.

This section will assist the technician in Always perform the indicated procedures in the
identifying and eliminating the source of a steer order listed in the chart. The steps are organized
axle shimmy and/or resonant ride complaint. so that the most likely causes are evaluated first
using the easiest and quickest tests. Steps which
Using the procedures outlined here, problems of require time-consuming measurements or
this nature will be systematically diagnosed and mechanical work are grouped toward the end of
corrected. the chart.

A form follows this section which should be used Periodic road tests are suggested during the
with the instructions. Make copies of this procedures in Chart No. 1 to determine if any
“Ride/Handling/Steering Evaluation adjustments made have corrected the problem.
Worksheet,” and use it to record your
findings. The completed worksheet should then The Vehicle Inspection and Measurement
be attached to the shop work order and retained procedures listed in the chart are explained in
for future reference. detail in the text which follows the chart.

Chart Nos. 2, 3 and 4 are included to aid the

Identify the Complaint technician in checking and adjusting wheel
runout. The explanation of the procedures in
Chart No. 1 continues after Charts 2, 3 and 4.
(ROAD TEST)
The first step in treating any problem is to
properly identify the complaint. A road test should
be performed with loading and roads typical of
those present when the problem is noticed by the
customer.

Steer Axle Shimmy is described as prolonged

steering wheel vibration which occurs
spontaneously at certain vehicle speeds or in
response to striking a bump. Changing vehicle
speed may cause shimmy to stop. Shimmy may
be present on smooth or rough roads.

Resonant Ride is noticed under similar

conditions. However, this vibration is felt through
the cab or seat instead of the steering wheel.

While vibration in a commercial vehicle can

originate in a variety of locations, steer axle
shimmy and/or resonant ride complaints can
typically be traced to the imbalance or excessive
runout of a rotating wheel end assembly.

Page 51
 TROUBLESHOOTING
26

Figure 26 — Chart No. 1: Vehicle Inspections and Measurements

Page 52
 TROUBLESHOOTING
Vehicle Inspections and SUSPENSION INTEGRITY
Measurements Procedures Look for broken or sagging springs, damaged or
worn spring eye and shackle bushings, loose
bolts or loose spring clips. There should be no
CORRECT PARTS INSTALLED evidence of movement between the
The vehicle should be assembled per original axle/spacer/springs.
specifications, and any modifications should be
returned to stock condition if possible. Check the condition of the shock absorber
bushings, and look for shock absorber leaks.

TIRE CONDITION AND WEAR PATTERNS Rear suspension components should also be
Check for tire flat spots, tire casing damage, or inspected.
28
improper tire mounting (beads not seated).

Other irregular tire wear patterns may give clues

as to the cause of the complaint.

STEERING SYSTEM LOOSENESS

Check for play in the steering column/shaft
(above the steering gear). Check all linkage and
components in the steering system (below the
steering gear) by lifting each front wheel and
looking for looseness by moving the wheel.

Check kingpin adjustment by measuring

clearances between the steering knuckle and the
top and bottom of the axle beam. Refer to
“STEERING KNUCKLE MEASUREMENTS AND
ADJUSTMENTS” on page 82.

Verify correct wheel bearing adjustment. Figure 28 — Suspension Components

27

ISOLATOR INTEGRITY AND BOLTS

Look for evidence of damage to the isolators.
This would include damage to the isolator rubber
(worn, torn, cut, “melted”), missing parts, isolators
that have been modified, or broken isolator
bracketry.

Evidence of isolator motion does not necessarily

mean that the isolator has failed. In particular, the
bottom piece of the engine front mount on the CH
chassis is made to slide slightly, and will “polish”
a small area on the bottom of the engine front
support crossmember. Make sure all isolator
bolts are installed and tight.

ROAD TEST: If any changes were made due to

the preceding inspections, a Road Test
should be run to determine whether the
problem has been corrected.
Figure 27 — Steering Linkage

Page 53
 TROUBLESHOOTING
WHEEL ASSEMBLY RUNOUT Wheel rim runout for both spoke and disc wheels
is measured with the tip of the tire runout gauge
Radial runout is very important, since harmonic
riding against the wheel rim as described below:
forces from excessive radial runout can be
greater than those from imbalance. The effects of
Tubeless rims — Check lateral runout with the
lateral runout are generally not as severe.
runout gauge tip against the drop center portion
of the rim, and radial runout at the tire bead seat
Before measuring runout, the vehicle should be
as shown in Figure 30. When checking radial
driven 15–20 miles. Promptly after driving, lift the
runout, check both bead seats.
tires off the ground to prevent flat spots (tires 30
begin to flat spot after 15 minutes of sitting still).

Before checking tire/wheel rim runout, tighten the

wheel nuts to specifications (refer to the
Maintenance and Lubrication Manual, TS494, for
wheel torque procedures and specifications).
With the wheels still on the vehicle, use a tire
runout gauge to check both lateral and radial
runout.

Total lateral runout should be checked on a

smooth surface in the tire upper sidewall, and
total radial runout should be checked on a
smooth rib in the center of the tread as shown in
Figure 29.
29
Figure 30 — Measuring Wheel Rim Runout on Tubeless
Rims

1. Wheel Lateral Runout 2. Wheel Radial Runout

Tubetype rims — Check lateral runout with the

runout gauge tip against the fixed side flange, not
at the edge/tip of the flange, and radial runout at
the tire bead seats as shown in Figure 31. When
checking radial runout, check at both bead seats.
31

Figure 29 — Measuring Total Lateral and Radial Runout

1. Total Lateral Runout 2. Total Radial Runout

Figure 31 — Measuring Wheel Rim Runout on Tubetype

Rims

1. Wheel Lateral Runout 2. Wheel Radial Runout

Page 54
 TROUBLESHOOTING
Maximum runout values are as follows: At a minimum, static balancing of each tire/rim
assembly should be done. If the spin balancing
Bias Ply Tires Radial Ply Tires technique is used, move rear tires to the front for
Lateral Runout 0.110″ (2.8 mm) 0.095″ (2.4 mm) balancing.
Radial Runout 0.110″ (2.8 mm) 0.095″ (2.4 mm) Remove all weights from each wheel before
balancing. When adding weights, add equal
For spoke wheels, first correct lateral runout by amounts to the inside and outside of the rim, if
adjusting the wheel lugs, then check radial possible. In many instances, adding weights to
runout. Refer to Chart No. 2 for the proper the inside of the rim will not be possible because
procedure. Correct wheels on the steer axle first. of insufficient clearance between the rim and the
tie rod ends. Before adding weights to the inside
For disc wheels, correct radial runout first. This is of the rim, ensure that there is sufficient
because “match mounting”may be required to clearance between the rim and the tie rod end.
correct radial runout problems with disc wheels. No more than 18 ounces of weight should be
Match mounting establishes the relative position applied to any one assembly. If more weight is
of the tire with respect to the rim. Lateral runout required, the tire should be broken down, turned
should be checked after the match mounting on the rim, and rechecked.
procedure.
If an imbalance problem persists, dynamic
Use Chart No. 3 when checking radial runout, balance should be checked. This can be done by
and Chart No. 4 when checking lateral runout on taking the tire/rim assemblies to a shop that is
disc wheels. Correct wheels on the steer axle capable of two-plane balancing (often called
first. computer spin balancing). At a minimum, the
front wheels should be balanced, and the rears
should also be done if possible. After the wheels
WHEEL ASSEMBLY BALANCE
have been balanced by an outside shop, they
Both static (single plane) and dynamic (two should be spun again on the vehicle to make sure
plane) balance of the wheel assembly are that a balance problem does not exist with the
important. hubs and drums.

Two static balancing methods are possible: ROAD TEST: If any changes were made due to
the preceding inspections, a Road Test
앫 Spin the wheel assembly on the truck, and
should be run to determine whether the
use a vibration pickup and strobe to locate
problem has been corrected.
wheel weights.
앫 Use a bubble balancer.

Page 55
 TROUBLESHOOTING
32

Figure 32 — Chart No. 2: Checking Spoke Wheel Radial Runout

Page 56
 TROUBLESHOOTING
33

Figure 33 — Chart No. 3: Checking Disc Wheel Radial Runout

Page 57
 TROUBLESHOOTING
34

Figure 34 — Chart No. 4: Checking Disc Wheel Lateral Runout

Page 58
 TROUBLESHOOTING
CHASSIS ALIGNMENT If any changes were made due to the
preceding inspections, a Road Test should be
Caster and toe should be checked. Refer to the
run to determine if the problem has been
specifications in the Maintenance and Lubrication
corrected.
Manual, TS494. Set toe at the low end of the
specification for radial tires. Other chassis
alignment specifications have a minimum effect
on shimmy, but should be checked, if possible,
when the problem is persistent.

Page 59
 TROUBLESHOOTING
Ride/Handling/Steering Evaluation Worksheet
Make a copy of the following form and use it to record results of vehicle inspections and measurements.
35

Figure 35 — Ride/Handling/Steering Evaluation Worksheet

Page 60
MAINTENANCE

MAINTENANCE

Page 61
 MAINTENANCE
STEERING SYSTEM LUBE INTERVALS
MAINTENANCE Refer to the Maintenance and Lubrication
manual, TS494, for additional information
concerning chassis vocation, lubrication intervals
and other lubrication recommendations and
requirements.
Beginning December 2005, Mack Trucks, Inc.
began phasing DEXRON® III into production as Lubricate all suspension components with MG-C
the factory fill for the power steering system. grease.
Vehicles utilizing DEXRON®-type automatic
transmission fluid in the power steering system
are identified by the label affixed to the power POWER STEERING FLUID CHANGE
steering reservoir. When adding fluid to the
power steering system, always check the label on
the side of the reservoir and be sure to use the
correct fluid. To keep dirt from entering the system, clean
around fittings and both hose connections at the
steering gear. Also clean around the reservoir
General maintenance procedures for MACK cover.
components are detailed in the Maintenance and
Lubrication Manual, TS494. For periodic 1. Before changing the power steering fluid,
maintenance instructions and intervals, refer to drive the vehicle until the engine coolant
this manual, which is supplied with the chassis. reaches normal operating temperature. Shut
This manual is published by the MACK Service down the engine.
Publications Department, and is available for
2. Position drain pans under the vehicle, and
purchase through your nearest MACK dealership.
disconnect the pressure and return lines at
Axle alignment specifications are also given in
the steering gear. This allows the power
the Maintenance and Lubrication Manual, TS494.
steering reservoir and hoses to drain.
3. Jack up the front end so the wheels can be
Steering Maintenance steered manually. Steer several times from
left steering stop to right steering stop. This
At each A, B, C and D inspection interval, inspect pumps the remaining power steering fluid
steering linkages, including steering shaft U-joints out of the system.
and yokes, drag link and cross steering tubes for 4. Replace the steering system filter as
damage or looseness. Also, check ball sockets required. Two different types of filters are
for boot damage, looseness or wear. Also, at the used in the steering system, each of which
same intervals, check the condition of the has a different change interval. Change
steering gear mounting brackets and check all intervals for the different filters are as
fasteners for looseness. Inspect the steering follows:
gear, hoses, pump and reservoir for leaks. Check
the fluid level in the power steering reservoir and 앫 Standard Cellulose Filter — changed
add the specified fluid if necessary. annually, at each power steering fluid
change.
At each C and D inspection interval, check that 앫 Synthetic Filter — changed every
the steering shaft pinch bolts are tightened to 3 years or 300,000 miles/483 000 km
specification (refer to “Steering Shaft Universal for vocational chassis, or every 5 years
Joint Pinch Bolts” on page 110 in the or 500,000 miles/805 000 km,
SPECIFICATIONS section). Replace any pinch whichever occurs first.
bolts that are corroded or damaged. Before installing the filter, clean the inside of
the reservoir with a clean, lint-free shop
At each D inspection interval, change the power cloth.
steering fluid.
5. Reconnect the pressure and return lines,
and fill the reservoir with the recommended
fluid.

Page 62
 MAINTENANCE
Steering Gear Bleed Procedures

Always check the label located on the power Air must be bled from the steering system
steering reservoir to identify which fluid anytime steering gear(s), assist cylinder (if
(DEXRON® or engine oil) should be used to refill equipped), power steering pump or steering
the power steering system. hoses are replaced, or if any steering hoses were
disconnected and the system lost fluid. Bleed
procedures for the different steering gears are as
6. Bleed the air from the steering system. Refer follows:
to the procedures under the heading
“Steering Gear Bleed Procedures.” TRW and Sheppard Steering Gears with
Auto-Bleed Feature

Make sure that the reservoir does not run dry

during the purging operation, as air may be drawn An auto-bleed feature was initially incorporated
into the system. into Sheppard M100 and M90 steering gears.
M100 and M90 steering gears having the
7. Lower the chassis to the ground. auto-bleed feature are identified by the word
8. Start the engine and steer the wheels “AUTO” cast into the housing, whereas
several times from the left steering stop to manual-bleed M90 and M100 steering gears are
the right steering stop. identified by the bleeder screw located in the
steering gear housing above the pitman arm
9. Check the reservoir and add fluid, if shaft. All Sheppard M110 and SD110 steering
necessary. gears incorporate the auto-bleed feature.

Air in Steering System For manual-bleed Sheppard gears, it is VERY

IMPORTANT that the proper bleed procedures
Momentary “hard spots” may be felt in the be used. Refer to the procedures outlined under
steering system. This condition is usually caused the heading “Sheppard Manual-Bleed Steering
by air that has become trapped in the system. Gears.”
Additionally, this condition can be accompanied
by “wheel kick” when one tire hits a pothole or 1. Check the fluid level in the reservoir and
similar road imperfection. Typically the vehicle replenish with the recommended power
operator will complain of a “hard spot,” “high spot” steering fluid.
or “hard steering.”

In addition to momentary “hard spots,” air in the

power steering system could result in a shimmy Always check the label located on the power
that intensifies when rough roads are steering reservoir to identify which fluid
encountered. (DEXRON® or engine oil) should be used to refill
the power steering system.
If air in the steering system is suspected, the
system should be bled. Additionally, the steering
system should be bled if the steering gear(s),
assist cylinder (if equipped), power steering pump
or steering hoses are replaced, the steering fluid Make sure the reservoir does not run dry during
has been changed or if the steering hoses were the purging operation as air may be drawn into
disconnected and the system lost fluid. For the system.
steering system bleeding procedures, refer to the
section “Steering Gear Bleed Procedures.” 2. Raise the front of the vehicle so that the front
wheels are off the ground. Place jackstands
of adequate capacity under the front axle
beam to support the vehicle.

Page 63
 MAINTENANCE
36

Do not work on or around a raised vehicle that

is supported only by a hydraulic jack, as the
jack can fail suddenly and unexpectedly,
resulting in severe personal injury or death.
Always use jackstands of adequate capacity
to support the weight of the vehicle.

3. Start the engine and steer the wheels

several times from left to right steering
stops.
4. Check the fluid level in the reservoir and
replenish as necessary.
5. Lower the vehicle to the ground.

Sheppard Manual-Bleed Steering Gears

1. Check the fluid level in the reservoir and
replenish with the recommended fluid as
necessary. Figure 36 — Sheppard Steering Gear Bleeder Screw
Location

1. Bleeder Screw
Always check the label located on the power
steering reservoir to identify which fluid 4. Using a 1/8″ Allen wrench, open the bleeder
(DEXRON® or engine oil) should be used to refill screw 2–3 turns.
the power steering system.
5. Turn the steering wheel to a full right turn.
2. With the wheels on the ground, start the 6. Close the bleeder screw when the wheels
engine and turn the steering wheel to a full are turned fully to the right.
left turn.
3. Locate the bleeder screw in the steering
gear. The bleeder screw is located in the
steering gear housing, above the pitman Turning the wheels to a full right turn with the
arm shaft. bleeder screw open forces air under pressure
from the steering system. DO NOT steer the
wheels to the left with the bleeder screw open, as
this will draw air back into the system.

7. Repeat the above procedures 2–3 times

until a smooth stream of oil flows from the
bleeder port. A smooth stream of oil
indicates that all the air has been purged
from the system.

Make sure the reservoir does not run dry during

the purging operation, as air may be drawn into
the system.

Page 64
 MAINTENANCE
8. When a smooth stream of fluid flows from KINGPIN LOWER BUSHING
the bleeder port, close the bleeder screw
With the vehicle raised off the ground and
and tighten.
supported on jackstands, lubricate the kingpin
9. Check the fluid level in the reservoir and lower bushing. Raising the vehicle off the ground
replenish with the recommended fluid as ensures that grease will fill the areas around the
necessary. kingpin and bushing. Apply the recommended
chassis lubricant to the lower bushing grease
fitting until grease purges from the joint between
Power Steering Hoses the lower steering knuckle and the lower portion
of the axle eyelet. Ensure kingpin lower
Typically, power steering systems operate at bushing is lubricated with the front of the
pressures exceeding 2,000 psi, and in some vehicle raised off the ground and supported
applications, system pressure may be as high as on jackstands of adequate capacity.
2,700 psi. When existing power steering hoses
must be replaced, the replacement hose must be
equivalent (No. 8 hose with crimped-on hose
fittings) to the factory-installed hoses. Do not work under a vehicle that is supported
Preassembled hoses for the most popular power only on a hydraulic jack. The hydraulic jack
steering system combinations are available could fail suddenly and unexpectedly,
through the MACK Parts System. resulting in severe personal injury or death.
Always use jackstands of adequate capacity
Kingpin Lubrication Procedures to support the weight of the vehicle.
Refer to the Maintenance and Lubrication
Manual, TS494, for additional information
KINGPIN UPPER BUSHING concerning chassis vocation, and other
With the vehicle weight on the ground, apply the lubrication recommendations and
recommended chassis lubricant to the upper requirements.
bearing grease fitting until grease purges from
the joint between the upper steering knuckle and
the upper portion of the axle eyelet. Ensure
kingpin upper bearing is lubricated with
vehicle weight on the ground.

Page 65
 NOTES

Page 66
REPAIR INSTRUCTIONS

REPAIR INSTRUCTIONS

Page 67
 REPAIR INSTRUCTIONS
STEERING SYSTEM GENERAL
37

INSPECTIONS

Steering (Turning) Angle and

Turning Radius
Correct setting of the turning angle is important. A
steering angle that is too large can cause
interference between the tires and the chassis or
steering linkage. In some cases, excessive
steering angle could cause a dangerous steering
linkage toggle condition that could lock the
steering and cause a loss of vehicle control. If the
steering angle is too small, the maneuverability of
the vehicle is reduced and the turning radius
increases. Figure 37 — Checking for Broken or Sagging Springs
38

On all vehicles, the front axle wheel stops must

be adjusted to provide a minimum of one-inch
clearance between the tires and chassis
components, and a minimum of one-half inch
between any moving steering component (pitman
arm, drag link, steering lever, etc.) and any other
steering component.

Check the turning angle whenever the wheels are

aligned or if new springs or front axle have been
installed. The turning angle must be adjusted for
Figure 38 — Torquing Spring Clips
both right- and left-hand turns. The angle for a 39
right-hand turn may not be the same as for a
left-hand turn. If wheel stop adjustments are
made on a vehicle, the steering gear pressure
relief poppets must also be adjusted. Refer to
“FRONT AXLE AND STEERING
ADJUSTMENTS” on page 72 and “STEERING
GEAR ADJUSTMENTS” on page 77, to ensure
proper adjustments.

Springs
Vehicle stability suffers if the springs do not keep
the front and rear axles in alignment. Check for
broken or sagging springs, loose spring clips or
rebound clips, loose axle clamping plates, and
front spring center bolt wear (indicated by the
loose fit of the bolt). Refer to Frame, Springs and Figure 39 — Checking Axle Clamp Plates
Suspension, 14-100, for recommended torque of
spring clips.

Page 68
 REPAIR INSTRUCTIONS
Excessive side clearance on the shackle end of Steering Linkage (Cross Steering
the spring may result in shimmy. Be sure that the
pin and bushing at the fixed end of the spring are Tube, Drag Link and Steering
a good fit. Clearance should not exceed Levers)
0.030 inch (0.8 mm). Looseness in this area
contributes to increased tire wear and tramp. Inspect all steering linkage for cracks, dents or
40
bends. Also make sure that the cross steering
tube clamp bolts are tightened to specification.
Repair or replace as necessary.
41

Figure 40 — Checking for Excessive Side Clearance

Figure 41 — Inspect Steering Linkage

Page 69
 REPAIR INSTRUCTIONS
BALL SOCKETS (TIE ROD ENDS) 6. Check that the ball socket nut is installed
and secured with a cotter pin.
When inspecting ball sockets, the front of the
vehicle must be raised off the ground. Support
the vehicle weight with jackstands of adequate
capacity.
A cotter pin must be installed through the
threaded end of the ball socket stud and the
nut must be tightened to proper specification.
A missing cotter pin can allow the ball socket
Never work on a vehicle that is supported
stud and nut to loosen and possibly result in
only by a hydraulic jack. The jack could fail
a total loss of steering control.
unexpectedly, resulting in severe personal
injury.
7. If a cotter pin is missing, check the ball
socket nut to make sure it is tightened to
1. Place blocks at the rear wheels and set the
specification (refer to Figure 79). Always
parking brakes to prevent the vehicle from
tighten the nut to the specified torque. If the
moving.
nut does not align with the cotter pin hole,
2. Raise the front of the chassis and support on continue tightening until the cotter pin can be
jackstands. inserted through both the nut and the end of
the ball socket stud. Do not loosen the nut in
3. Start the engine. Then have an assistant
order to install the cotter pin.
turn the wheels from full left to full right and
then return the wheels to the straight-ahead 8. Inspect the ball socket to ensure that the
position. While the wheels are turning, check socket is threaded correctly into the cross
for looseness in any threaded joint, or steering tube and that threaded engagement
unintended movement of any ball socket is deeper than the slot in the tube. Threads
stud or stud nut. Any movement requires of the ball socket must be visible for the
that the ball socket be replaced. entire length of the cross steering tube slot.
4. Shut the engine off.
5. Check all ball socket boots. Replace any ball
sockets that have missing, cracked or The ball socket must have adequate thread
damaged boots. engagement with the cross steering tube.
42

43

Figure 42 — Damaged Ball Socket Boot

Figure 43 — Ball Socket Thread Engagement
1. Socket Boot
1. Cross Steering Tube 3. Cross Steering Tube Slot
2. Tie Rod Threads Visible
Entire Length of Slot

Page 70
 REPAIR INSTRUCTIONS
9. Grasp the ball socket with both hands, as Axle Center Section
close as possible to the socket (no further
than approximately six inches). Apply The axle must be without bends or twists, and
pressure vertically (up and down) in a kingpin inclination should agree with the value
push/pull motion several times. Check for given in “FRONT AXLE SPECIFICATIONS” on
any movement or looseness of any ball page 109. The axle straightness is checked with
socket. Any movement (other than the axle and knuckles removed from the chassis.
rotational) greater than 1/8 inch (3 mm) No service is required, or possible.
between any linkage member and its
attachment point, requires that the ball
socket be replaced. Front End Alignment
10. Lubricate the ball sockets with MG-C grease
at each lubrication interval, as outlined in the If front end alignment requires adjustment, refer
Maintenance and Lubrication Manual, to Frame, Axle and Suspension Service and Total
TS494. Vehicle Alignment, 14-103, for the correct
procedures. Alignment specifications can be
found in the Maintenance and Lubrication
Frame Manual, TS494. Total chassis alignment is the
basis for vehicle stability, ease of steering,
Front and rear wheels must track correctly. To improved tire life, and satisfied drivers.
accomplish this, the front axle must be parallel to
the rear axle and at right angles to the center line
of the chassis. Refer to Frame, Axle and
Suspension Service and Total Vehicle Alignment,
14-103, for more information regarding axle
adjustment. Alignment specifications can be
found in the Maintenance and Lubrication
Manual, TS494

Steering Knuckle
Wear can occur between the knuckle bushing
and/or needle bearing and kingpin. If, during
inspection or adjustment, it is determined that
wear between the knuckle bushing and/or needle
bearing and kingpin is excessive, or proper
clearances cannot be obtained, the steering
knuckle must be overhauled. Excessive
clearance affects steering and increases tire
wear. Repairs must be made by replacing the
kingpin, bushings or bearings as required.

When replacing the knuckle bushings on the

FA23 front axle, it will be necessary to ream the
bushings to maintain proper clearances between
the kingpin and the bushings. Special reamers
are available for this purpose. Refer to “FRONT
AXLE AND STEERING SPECIFICATIONS” on
page 108 for kingpin and bushing specifications.
All other knuckle assemblies use presized
bushings, so reaming the bushings will not be
necessary. For adjustments and repairs related to
front axle components, refer to adjustment and
overhaul instructions.

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 REPAIR INSTRUCTIONS
FRONT AXLE AND STEERING Turning angle may be changed per customer
preference. Turning angle is changed by
ADJUSTMENTS adjusting the knuckle stop bolts. Adjust the stop
[422] bolts as necessary, until the desired turning angle
is achieved.
44

Knuckle Stop Bolt Adjustment

(Turning Circle)
1. Drive the vehicle straight into the service bay
and make sure the front wheels are facing
straight ahead.
2. Block the rear wheels to prevent the vehicle
from moving.
3. Raise the front of the chassis.
4. Place turning angle plates under each front
wheel, centered below each front tire. Make
sure the gauges on both plates are set to
zero.
5. Lower the front of the vehicle so that the
front tires and weight of the vehicle are
resting on the turning plates.
6. Start the engine and let it run at idle.
7. Use the treadle valve to apply the service
brakes. Figure 44 — Knuckle Stop Bolt Adjustment

When the desired turning angle is obtained, verify

that there is a minimum of one inch (25.4 mm) of
It is important that the service brakes be applied clearance between the tire and chassis
during this procedure, to prevent the front wheels components, and a minimum of 1/2 inch
from rotating while being turned. (12.7 mm) of clearance between any movable
steering and axle components and any other
8. Turn the steering wheel fully to the right until chassis components. Additionally, knuckle stops
the knuckle stop bolt contacts the axle. must be adjusted so that contact with the axle is
made at least one full thread before the steering
9. Read the amount of turn in degrees on the gear bottoms.
gauge of the right-hand turning angle plate.
10. Turn the steering wheel fully to the left until
the knuckle stop bolt contacts the axle.
After the knuckle stop bolts have been adjusted,
11. Read the amount of turn in degrees on the adjust the power steering gear internal pressure
gauge of the left-hand turning angle plate. relief poppets (refer to “TRW/TAS Series Power
Steering Gear Relief Poppet Adjustment” on page
73 and “STEERING GEAR RELIEF POPPET
ADJUSTMENT” on page 73).

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 REPAIR INSTRUCTIONS
STEERING GEAR RELIEF 3. If the output shaft timing mark is off center,
remove the drag link from the bottom of the
POPPET ADJUSTMENT pitman arm, and then reset the steering gear
to center. When the gear is centered and the
TRW/TAS Series Power Steering front wheels are straight ahead, adjust the
Gear Relief Poppet Adjustment drag link length until the ball stud fits into the
pitman arm.
Pressure relief poppets in TRW/TAS Series
steering gears may require readjustment if:
앫 Vehicle turning angle has been reduced.
On some chassis, drag links are not adjustable.
앫 Pitman arm was mistimed and has been
corrected.
4. Recheck the knuckle stop bolt adjustment
앫 Steering gear has been installed on a for proper turning angle.
different truck.
5. Reset the pressure relief poppets as follows:
Poppets are pressure unloading valves that must
be set to actuate just before a full turn has been a. Remove the steering gear fixed stop
reached in either direction. In this way, they bolt and install the adjusting screw
protect the steering system by relieving hydraulic (adjustment screw tool kit part No.
pressure before knuckle stops are contacted. 6990-O21407X1). Turn the adjusting
screw all the way in until flush with the
Once the knuckle stops have been set to ensure top of the jam nut.
proper clearances, and toggle angle has been
reviewed, you can use the following procedure for b. Raise the front wheels off the ground.
any necessary adjustment of the poppets. Support the front of the vehicle on
suitable heavy-duty jackstands of
adequate capacity to support the
weight of the vehicle.
If the knuckle stops are adjusted so you cannot c. Start the engine.
get at least 1-3/4 steering wheel turns in each
d. Turn the steering wheel in the direction
direction from the straight-ahead position, the
that causes the output shaft timing
poppets will not function.
mark to move toward the adjustment
screw (this varies by vehicle, and
depends upon the steering gear
mounting position). When the steering
wheel is turned in the proper direction,
TRW/TAS steering gears no longer have the
the steering gear piston rack moves
pressure relief poppet adjustment screws
toward the lower end of the steering
installed in the bottom cover assembly. Adjusting
gear.
the poppets requires an adjustment screw tool kit
(MACK part No. 6990-O21407X1).

1. With the chassis parked on a level surface,

steer the front wheels to the exact
straight-ahead position.
2. Check that the steering gear output shaft
timing mark aligns with the chisel mark
located on the steering gear housing. The
steering gear is centered when the two
timing marks are aligned with each other. If,
however, there is no visible timing mark on
the housing, the gear is centered when the
timing mark on the output shaft is
perpendicular (90 degrees) to the bore of the
steering gear.

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 REPAIR INSTRUCTIONS
e. Pull hard on the steering wheel. This Sheppard Power Steering Gear
forces the lower poppet seat against
the adjusting screw. This in turn causes Relief Poppet Adjustment
the lower poppet seat to contact the (Manual-Type)
push tube and forces it against the
upper poppet seat forcing it out. The Before performing the poppet adjustment, adjust
upper poppet seat will now be and lock the knuckle stop bolts to provide a
automatically set when the steering minimum of one-inch (25.4-mm) clearance
wheel is turned fully in the opposite between the tire and chassis components, and a
direction. minimum of 1/2-inch (12.7-mm) clearance
f. Turn the steering wheel in the opposite between any movable steering and axle
direction. Then pull hard on the steering component and any other chassis component.
wheel. This sets the upper poppet seat Knuckle stops must be adjusted so contact is
to the original factory setting. The made at least one full thread before the gear
poppet components are forced together bottoms.
to cause the push tube against the
lower poppet seat, pushing it out.
g. Shut off the engine.
If the gear bottoms before the steering stops are
h. Back out the adjusting screw one inch encountered in either a right-hand or left-hand
past the jam nut. turn, check pitman arm position. The timing
marks on the output shaft and the pitman arm
i. Start the engine.
must align. A maximum drag link to pitman arm
j. Turn the steering wheel in the direction toggle angle of 170 degrees must be maintained
that moves the steering gear piston with the gear bottomed in a full right turn for
rack toward the lower end of the left-hand steering gear (full left turn for right-hand
steering gear housing (same direction steering gear) with the front axle hanging free
as step “d”). Turn the steering wheel (front wheels off the ground).
until the knuckle stop bolt contacts the
axle.
k. Shut off the engine.
l. Turn the adjusting screw in until it The pitman arm must not be arbitrarily
stops. repositioned so the timing marks are not
aligned.
m. Back the adjusting screw out
3-1/4 turns. Then tighten the jam nut to
33–37 lb-ft (44.7–50.2 N폷m). The 1. Loosen the jam nuts that lock the adjustable
adjusting screw remains in this position plungers on the steering gear, if applicable.
until it becomes necessary to readjust Plungers without a jam nut have a
the relief poppets. The fixed stop bolt self-locking feature.
originally removed from the end of the 2. Turn the plungers in until they bottom.
steering gear is not to be reused.

One plunger is located on top of the gear, near

the input shaft. The other plunger is located on
the bottom of the gear.

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 REPAIR INSTRUCTIONS
3. With the chassis on the ground and the front Adjustment After Installation of a
wheels in the straight-ahead position, start Replacement Steering Gear
the engine and allow it to run at idle speed.
4. Turn the steering wheel to the left until the
plunger opens the relief valve. DO NOT
FORCE THE STEERING WHEEL! The If a replacement Sheppard steering gear is being
valve opening can be felt at the steering installed on a chassis, DO NOT turn the steering
wheel as the ease of steering suddenly gear input shaft, as the auto plungers can be
disappears. moved mechanically. The auto relief plungers are
set for minimum wheel cut prior to shipment.
5. Check the clearance at the left-hand knuckle
stop. An actual clearance should be Prior to setting the auto relief plungers, front
observed. wheel stop adjustment must be checked to be
sure a minimum of 1″ (25.4 mm) between the
6. Turn the plunger out to reduce the tires and chassis components, and a minimum of
clearance. Continue to adjust while turning 1/2″ (12.7 mm) clearance between any moving
the steering wheel to the left, until a 0.06- to steering component (pitman arm, drag link,
0.12-inch (1.6- to 3.2-mm) clearance is steering lever, etc.) and any other steering
obtained. If the plunger has a jam nut, lock it component is provided. For wheel stop
in position. adjustment procedures, refer to “KNUCKLE
STOP BOLT ADJUSTMENT (TURNING
CIRCLE).”

On gears having plungers without jam nuts, do 1. Apply the parking brakes and block the rear
not back the plunger out beyond 1/16″ (1.6 mm) wheels to prevent the vehicle from moving.
below the face of the housing boss, as leakage
may result. 2. Raise the front of the vehicle so that the front
wheels are off the ground and support the
vehicle on jackstands of adequate capacity
7. Repeat this procedure to obtain the same
to support the weight of the vehicle.
clearance in a right-hand turn.

Sheppard Power Steering Gear

Relief Poppet Adjustment Always support the vehicle on jackstands of
adequate capacity to support the weight of
(Automatic-Type) the vehicle. Do not work on or around a
vehicle that is supported only by a hydraulic
Beginning with the M90 and M100 Series of jack, as the jack can fail unexpectedly, at any
steering gears, Sheppard steering gears were time, resulting in serious personal injury or
made available with auto relief plungers. Auto death.
relief plungers provide a maintenance-free
installation with no need for future adjustments. 3. Start the engine.
The M90 and M100 steering gears with the auto
bleed/auto relief plunger features are visually 4. With the engine running, turn the steering
identifiable by the word “AUTO” cast into the side wheel to full lock in both the left- and
of the housing. The later models of Sheppard right-hand directions. When the end of travel
steering gears (M110 and SD110) used on all is reached in each direction, pull on the
MACK models utilize the auto bleed/auto relief steering wheel to ensure that the auto
plunger features. Procedures for adjusting the plunger is properly set.
auto relief plungers are as follows:

The steering knuckle must contact the axle stops

to properly set the auto plungers.

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 REPAIR INSTRUCTIONS
5. After the auto plungers have been set, stop 6. Raise the front of the vehicle so that the front
the engine and lower the vehicle to the wheels are off the ground and support the
ground. vehicle on jackstands of adequate capacity
to support the weight of the vehicle.
Readjustment of Auto Relief Plungers

Once adjusted, readjustments to the auto relief

plungers are not necessary unless tire size Always support the vehicle on jackstands of
changed or turning radius is reduced. adequate capacity to support the weight of
the vehicle. Do not work on or around a
vehicle that is supported only by a hydraulic
jack, as the jack can fail unexpectedly, at any
DO NOT adjust the auto relief plungers unless time, resulting in serious personal injury or
tire size is changed or turning radius is reduced. death.

1. Park the vehicle on a solid surface, apply the 7. Start the engine.
parking brake and block the rear wheels to
8. With the engine running, turn the steering
prevent the vehicle from moving.
wheel to full lock in both the left- and
2. Raise the hood or tilt the cab to access the right-hand directions. When the end of travel
steering gear. is reached in each direction, pull on the
steering wheel to ensure that the auto
3. Remove the plastic caps from both auto
plunger is properly set.
relief plunger ports.
4. Carefully insert a 1/4″ punch into the plunger
hole and use a small ball peen hammer to
drive the auto plunger into the housing until The steering knuckle must contact the axle stops
it bottoms in the bore. Use this procedure for to properly set the auto plungers.
both plungers.
9. After the auto plungers have been set, stop
the engine and lower the vehicle to the
ground.
Use care with the punch, and be sure there are
no sharp edges on the punch that could damage These tests are explained in the section “POWER
the plunger bore. A leak can occur if the bore is STEERING SYSTEM HYDRAULIC TESTS.”
damaged when using a punch to drive the auto
plungers into the bore.

5. Reinstall the plastic caps into the plunger

ports.

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 REPAIR INSTRUCTIONS
STEERING GEAR
ADJUSTMENTS
[411] One-half inch minimum clearance must be
maintained between any movable steering
and axle components and any other chassis
When a new vehicle is received from the factory,
component.
steering adjustments have been preset.
Adjustments to turning angle can be made to
satisfy customer requirements. Adjustments may
also be required if steering components are
replaced, or tire size is changed. In addition to the
Maintain at least one-sixteenth to
guidelines published in the steering gear
one-eighth-inch clearance between axle and
manufacturer service manual, always observe
knuckle stop bolt when pressure relief
the following:
occurs.

Maximum drag link to pitman arm angle with

the axle hanging free (wheels turned full right Whenever turning angle is changed, steering
or left, and off the ground) is 170 degrees. gear relief poppets must also be readjusted.

One-inch minimum clearance must be

maintained between tires and chassis
components.

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 REPAIR INSTRUCTIONS
Steering Gear Adjustments Chart
Refer to the specific steering gear manufacturer
service manual for instructions before performing
any of these operations.

STEERING GEAR ADJUSTMENTS CHART

Steering Gear Centering External Preload
Type of Steering Method* Poppet Adjustment Provisions Adjustments**
TRW/TAS65 and High Spot — Use Timing Automatic — Manual Adjustment, External Sector Shaft
TRW/TAS85 Marks or Readjustment for Less Travel Adjusting Screw
Requires Special Service Poppet
Adjusting Screw
Sheppard Gears (gears Full Travel Method, Use Fully Adjustable — Two External No Adjustments Required
without auto-poppets) Timing Marks — No High Screws or Possible
Spot
Sheppard Gears (with Use Timing Marks — No Automatic No Adjustments Required
auto-poppets) High Spot or Possible

* Center gear with vehicle front wheels in the straight-ahead position.

** Shaft preload adjustments not listed are accomplished internally by using shims or thrust washers.

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 REPAIR INSTRUCTIONS
Steering Gear Centering TRW/TAS POWER STEERING GEARS
1. Chassis steering geometry must be properly
This section covers the centering of power adjusted.
steering gears.
2. Front wheels must be positioned in the
The TRW/TAS integral power steering gears are straight-ahead position.
designed with a “high spot,” or no lash point, at 3. These gears are centered when the timing
the center of gear travel. In order to provide mark on the end of the output or sector shaft
proper steering performance, these gears must is perpendicular to the input or worm shaft.
be centered when the front wheels are in the
straight-ahead position.

The Sheppard integral power steering gears do On the TRW/TAS65 gears, do not rotate output
not have a “high spot.” However, it is still shaft more than 29 degrees (1.6 input shaft
important to center the Sheppard gears to ensure revolutions). Doing this resets the automatic
full turning angle in both directions. poppets.
45

Figure 45 — TRW/TAS65 Model Gear

1. Pitman Arm Timing Mark 2. Gear Housing Timing Mark

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 REPAIR INSTRUCTIONS
SHEPPARD POWER STEERING GEARS rotate the gear through its full range of travel,
(392S, 492S AND 592S) counting the number of turns required. Turn the
gear back one-half the total number of turns to
Sheppard 392S, 492S and 592S steering gears
place the gear in its center position. Align the
are centered when the timing mark on the end of
timing mark on the output shaft so that it is
the output shaft is perpendicular to the input
perpendicular with the center line of the input
shaft. As an alternate method of centering the
shaft.
gear, position the gear at one end of travel. Then, 46

Figure 46 — Sheppard Power Gears — 392S, 492S and 592S

1. Pitman Arm Timing Mark

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 REPAIR INSTRUCTIONS
SHEPPARD POWER STEERING GEARS DRAG LINK ADJUSTMENT (WHERE
(M90, M100P AND M110P) APPLICABLE)
These steering gears are centered when the With the front wheels in the straight-ahead
timing mark on the end of the output shaft is position and the steering gear centered, the drag
aligned with the timing mark on the gear housing. link must be adjusted to the required length when
In this position, the timing mark on the end of the installed. When the drag link has been properly
output shaft will be perpendicular to the center adjusted and securely fastened to the pitman
line of the input shaft. arm, the ball stud assembly freely enters the hole
47
in the steering lever. To ensure adequate thread
engagement, measure the drag link end (refer to
Figure 48).

To ensure adequate thread engagement of the

tie rod (ball socket), it must not extend out of
the drag link further than 3-3/32 inches with
the 1-1/2 inch ball (1-1/8 inch thread), or
3-13/16 inches with 1-3/4 inch ball (1-1/4 inch
thread). This measurement is taken from the
end of the drag link tube to the center line of
the tie rod. Refer to Figure 48.

Non-adjustable drag links are used on certain

MACK chassis.
48

Figure 47 — Sheppard Power Steering Gears —

M100P and M110P

1. Pitman Arm Timing Mark 2. Gear Housing Timing

Mark

Figure 48 — Measuring Thread Engagement of Tie Rod

Additionally, the socket stem should be threaded

into the tube past the end of the slot.

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 REPAIR INSTRUCTIONS
STEERING KNUCKLE
49

MEASUREMENTS AND
ADJUSTMENTS
[422]

Kingpin Lateral Play (FAW 12, 14.3,

16, 18[W], and 20[W] Axles)
Before replacing kingpins, bushings/bearings on
MACK front axles, kingpin lateral play must first
be checked with a dial indicator to verify
replacement of these components is actually
necessary. Kingpins, bushings and bearings
Figure 49 — Measuring Kingpin Upper Bearing Lateral
should be replaced only when lateral play Play (Chassis Right Side)
exceeds the specification of 0.015 inch
(0.381 mm). Procedures for measuring kingpin 50

lateral play are as follows:

1. Place blocks at the rear wheels to prevent
the vehicle from moving.
2. Raise the front of the vehicle off the ground
and support on jackstands of adequate
capacity.

Do not work under a vehicle that is supported

only on a hydraulic jack, as a hydraulic jack
could fail suddenly and unexpectedly,
resulting in severe personal injury or death.
Always use jackstands of adequate capacity Figure 50 — Measuring Kingpin Upper Bearing Lateral
to support the weight of the vehicle. Play (Chassis Left Side)

3. Measure kingpin lateral play at the upper b. Position the tip of dial indicator J 8001,
bearing as follows: or equivalent, against the upper portion
of the steering knuckle as shown in
a. Secure the dial indicator base
Figure 49 and Figure 50.
J 26900-13, or equivalent, to a flat
portion at the top of the axle beam as c. Zero the dial indicator.
shown in Figure 49.
d. Rotate the wheel so that a hand hole
(steel and aluminum disc wheels), or
space between spokes (spoke wheel)
is in the 12 o’clock position. Insert a pry
For the most accurate measurements, mount the bar through the hand hole (or the space
dial indicator on a surface of the axle beam that is between the spokes) and position on
as flat as possible. the top of the brake drum. Pull the pry
bar upward to move the wheel
assembly and knuckle while observing
the reading on the dial indicator. Use
care to prevent damaging or marring
the wheel surface with pry bar.

Page 82
 REPAIR INSTRUCTIONS
52

To ensure accurate measurements, do not allow

the steering knuckle to turn to the left or right
while moving the tire/wheel assembly. Having an
assistant apply the brakes will lock the wheel in
position and aid in preventing the steering
knuckle from turning.

A reading of greater than 0.015 inch

(0.381 mm) on the dial indicator
indicates that the upper bearing is worn
or damaged. Overhaul of the steering
knuckle is required (refer to
“STEERING KNUCKLE OVERHAUL”
on page 87) with the appropriate Figure 52 — Measuring Kingpin Lower Bushing Lateral
Play (Chassis Left Side)
kingpin rebuild kit.
4. Measure the kingpin lateral play at the lower b. Position the tip of dial indicator J 8001,
bushing as follows: or equivalent, against the lower portion
of the steering knuckle as shown in
a. Secure the dial indicator base Figure 51 and Figure 52.
J 26900-13, or equivalent, to a flat
portion at the bottom of the axle beam c. Zero the dial indicator.
as shown in Figure 51 and Figure 52. d. Rotate the wheel so that a hand hole
(steel and aluminum disc wheels), or
space between spokes (spoke wheel)
is in the 12 o’clock position. Insert a pry
For the most accurate measurements, mount the bar through the hand hole (or the space
dial indicator on a surface of the axle beam that is between the spokes) and position on
as flat as possible. the top of the brake drum. Pull the pry
51
bar upward to move the wheel
assembly and knuckle while observing
the reading on the dial indicator. Use
care to prevent damaging or marring
the wheel surface with pry bar.

To ensure accurate measurements, do not allow

the steering knuckle to turn to the left or right
while moving the tire/wheel assembly. Having an
assistant apply the brakes will lock the wheel in
position and aid in preventing the steering
knuckle from turning.

A reading of greater than 0.015 inch (0.381 mm)

Figure 51 — Measuring Kingpin Lower Bushing Lateral on the dial indicator indicates that the lower
Play (Chassis Right Side) bushing is worn or damaged. Overhaul of the
steering knuckle is required (refer to “STEERING
KNUCKLE OVERHAUL” on page 87) with the
appropriate kingpin rebuild kit.

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 REPAIR INSTRUCTIONS
Steering Knuckle Vertical Clearance To measure the clearance, place a thickness
gauge such as J 26900-8 or equivalent between
(FAW 12, 14.3, 16, 18[W], and 20[W] the steering knuckle and the axle beam eyelet as
Axles) shown in Figure 54. Measure at three locations,
approximately 90 degrees apart, around the axle
Steering knuckle vertical clearance must be beam eyelet.
54
checked and adjusted if necessary, at the first A
inspection when the chassis is new, and
thereafter, at each C and D inspection. Clearance
between the knuckle and the top of the axle
eyelet should be set between 0.005–0.027 inch
(0.127–0.686 mm) to provide a minimum
clearance of 0.020 inch (0.508 mm) between the
knuckle and the bottom of the axle eyelet. Failure
to maintain this clearance may result in
accelerated wear of the steering knuckle/axle
beam assembly.

Steering knuckle vertical clearance must be

measured with the vehicle on the ground, or if the Figure 54 — Measuring Steering Knuckle Upper
front of the vehicle is raised, with a jack placed Clearance
under the steering knuckle as shown in Figure 53,
to load the knuckle upward. 1. Measuring clearance between steering knuckle and
axle beam eyelet.
53

If the measurement is not between

0.005–0.027 inch (0.127–0.686 mm), adjust
vertical clearance as follows:
1. Place blocks under the rear wheels to
prevent the vehicle from moving.
2. Raise the front of the vehicle off the ground
and support on jackstands of adequate
capacity.

Do not work under a vehicle that is supported

only on a hydraulic jack, as a hydraulic jack
could fail suddenly and unexpectedly,
resulting in severe personal injury or death.
Always use jackstands of adequate capacity
to support the weight of the vehicle.

3. At the bottom of the steering knuckle,

Figure 53 — Loading Steering Knuckle Upward remove the cotter pin that secures the
adjusting screw.
4. Turn the adjusting screw clockwise to draw
the knuckle snug against the top of the axle
beam eye.

Page 84
 REPAIR INSTRUCTIONS
5. Once the knuckle is snug against the axle
55

beam, turn the adjusting screw

counterclockwise until the first cotter pin slot
aligns with the cotter pin hole. Recheck the
vertical clearance as described previously. If
upper clearance is not within range, turn the
adjusting nut an additional 1/4 turn
counterclockwise until the second cotter pin
slot aligns with the cotter pin hole. Recheck
the measurement.
6. After proper steering knuckle upper
clearance has been set, install a new cotter
pin to secure the adjusting nut in place.

When the steering knuckle upper clearance is

properly set between 0.005–0.027 inch Figure 55 — Measuring Steering Knuckle Lower
(0.127–0.686 mm), verify that the lower clearance Clearance
is at least 0.020 inch (0.508 mm) by measuring
the gap between the steering knuckle and the 1. Measuring gap between steering knuckle and axle
beam bottom.
bottom of the axle beam eyelet with a thickness
gauge as shown in Figure 55.
If proper vertical clearance cannot be obtained,
the steering knuckle must be overhauled. Refer
to “STEERING KNUCKLE OVERHAUL” on page
87 for overhaul procedures.

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 REPAIR INSTRUCTIONS
Steering Knuckle Bearing 56

Adjustment (FA 23 Axles)

This type of steering knuckle is used on all
23,000-pound MACK axles. A top-mounted roller
thrust bearing is used along with a tapered
kingpin to attach the knuckle to the front axle in
this assembly.

Figure 56 — MACK 23,000-Pound Axle Steering Knuckle Assembly

Adjustment of these knuckle assemblies is 5. After obtaining the proper clearance, install
required when dimension B is less than the washer and locknut. Tighten the locknut
0.005 inch (0.13 mm). to 100–150 lb-ft (136–203 N폷m). Install a
new cotter pin and bend both ends.
1. To adjust, first remove the knuckle top
cover. Then adjust, using the following 6. If it is determined that the proper clearances
procedure. cannot be obtained, the steering knuckle
must be overhauled. Refer to “STEERING
2. Remove the cotter pin, and loosen. Then
KNUCKLE OVERHAUL” on page 87.
remove the locknut and the taper nut lock
washer.
3. Tighten the taper (adjusting) nut until the
knuckle contacts the top of the axle eyelet.
4. Back off the nut to obtain between
0.005–0.020 inch (0.127–0.381 mm)
clearance between the knuckle and the top
of the axle eyelet (dimension A). This should
result in a clearance of less than 0.020 inch
(0.508 mm) between the knuckle and the
bottom of the axle eyelet (dimension B).

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 REPAIR INSTRUCTIONS
STEERING KNUCKLE
OVERHAUL
[422] Non-current production axles use an expansion
plug seal that is staked in place. These expansion
plugs should be replaced with a press fit seal
Disassembly — FAW 12, 14.3, 16, plug.
18(W) and 20(W) Front Axles
4. Remove the Allen plug from the jackscrew
hole located in the center of the seal plug.
These assemblies are typical of current MACK Then install a 7/16″-20 grade 5 bolt into the
front axles up to 20,000 pounds, and use a threaded hole until it contacts the top of the
tapered kingpin and a bottom-mounted thrust kingpin. Slowly tighten the bolt to push the
bearing. plug from the kingpin upper bore.
57
If it has been determined that the steering
knuckle must be overhauled, obtain the proper
knuckle overhaul parts kit which includes
bushings, bearings, seals and kingpins. Follow
the procedures outlined.

Whenever a vehicle is jacked up, use proper

heavy-duty axle stands under the chassis to
prevent personal injury or vehicle damage in
the event of jack malfunction or vehicle
tipping.

1. Place a jack under the center of the front

axle and raise the vehicle. Position
heavy-duty axle stands under the frame and
lower the jack to take the weight of the
chassis off of the front axle springs. Remove
the wheel and hub assembly.
2. Disconnect the drag link from the steering
lever and the cross steering tube from the
cross steering levers.
3. Remove the brake mechanism assembly
complete with the anchor plate or spider
assembly.
Figure 57 — Front Axle Sealing Plug

Wire the anchor plate or spider assembly to the

chassis. Do not allow assembly to hang by hose.

Page 87
 REPAIR INSTRUCTIONS
5. Remove the cotter pin which retains the
thrust bearing adjusting screw. Unscrew the
adjusting screw, using tool J 44004, being
careful when removing the screw, as the Steering knuckles built with the staked expansion
thrust bearing will be on top of the adjusting plug have four stake marks located on the top of
screw. the steering knuckle 90 degrees apart to assist in
retaining the expansion plug. These stake marks
6. Drive the kingpin out through the bottom of must be removed prior to installation of the press
the knuckle by using a brass drift and driving fit seal plug.
on the top of pin until the tapered kingpin
falls free. Lift the knuckle off the axle.
7. Clean the knuckle thoroughly. Be sure that
the lubrication holes are open.
8. Press the lower bushing from the knuckle.

Page 88
 REPAIR INSTRUCTIONS
Disassembly — FA 23 Front Axles 58

This type of steering knuckle is used on all

23,000-pound MACK axles. A top-mounted roller
thrust bearing is used along with a tapered
kingpin to attach the knuckle to the front axle in
this assembly.

Figure 58 — MACK 23,000-Pound Axle Steering Knuckle Assembly

If it has been determined that the steering 3. Remove the brake mechanism assembly
knuckle must be overhauled, obtain the proper complete with the anchor plate or spider
knuckle overhaul parts kit which includes assembly.
bushings, bearings, seals and kingpins. Follow
the procedures outlined.

Wire the anchor plate or spider assembly to the

chassis. Do not allow assembly to hang by hose.
Whenever a vehicle is jacked up, use proper
heavy-duty axle stands under the chassis to 4. Remove the top and bottom knuckle covers.
prevent personal injury or vehicle damage in
the event of jack malfunction or vehicle 5. Remove locknut cotter pin, locknut, lock
tipping. washer, taper nut washer, taper nut and
thrust bearing.
1. Place a jack under the center of the front 6. Place a piece of wood on top of the pin, and
axle and raise the vehicle. Position drive the pin out through the bottom of the
heavy-duty axle stands under the frame and knuckle. Lift the knuckle off the axle.
lower the jack to take the weight of the
7. Clean the knuckle thoroughly. Be sure that
chassis off of the front axle springs. Remove
the lubrication holes are open.
the wheel and hub assembly.
8. Press the upper and lower bushings out of
2. Disconnect the drag link from the steering
the knuckle.
lever and the cross steering tube from the
cross steering levers.

Page 89
 REPAIR INSTRUCTIONS
Reassembly — FAW 12, 14.3, 16, 9. Insert the kingpin into the knuckle assembly
from the bottom. Then use a bottle jack
18(W) and 20(W) Front Axles positioned against the bottom of the kingpin,
1. Check spindle portion of knuckle for wear to push the kingpin into the tapered eye of
caused by wheel bearings. Replace if the axle.
necessary. 10. With the bottle jack applying force against
2. Inspect brake hose and replace if the bottom of the kingpin, use a heavy
necessary. hammer to rap the top of the axle beam near
the knuckle, to drive and tightly wedge the
3. Install new presized bushings using a kingpin into the taper of the axle eye. A
hydraulic press or a hammer and correct heavy blow with a hammer will be necessary
size bushing drivers, taking care to line up to wedge the kingpin into the taper.
lubrication holes or grooves with those in the
knuckle. Bushings must be assembled with 11. Apply Never-Sieze®, or equivalent, to the
the groove runout toward the bottom. threads of the adjusting screw, and pack the
thrust bearing with grease. Then install
4. Install the new needle bearing. these two components into the knuckle.
5. Install the new oil seal. Adjust the steering knuckle vertical
clearance (refer to “STEERING KNUCKLE
MEASUREMENTS AND ADJUSTMENTS”
on page 82).
Never reuse the kingpin seal plug. Always install 12. Refer to “Kingpin Lubrication Procedures” on
a new plug. page 65 for lubrication of the kingpin
bushings and bearings.
6. Install the kingpin seal plug into the top of 13. Reinstall the brake mechanism, steering
the steering knuckle assembly by using a linkage and wheels. Refer to the Steering
hydraulic press to press the plug into the Component Torque Chart in the rear of this
bushing bore until the plug flange is seated manual and the following additional
against the knuckle. publications:
7. Apply a coating of Never-Sieze® (or 앫 Air and Brake System Service Manual,
equivalent) to the Allen plug threads. Install 16-104
the plug into the jackscrew hole.
앫 Wheels, Rims and Tires, 15-101
앫 Wheel Bearings Service Manual,
15-701
If the front axle is equipped with an expansion 14. Remove the axle stands, lower the vehicle
plug, replace it with a seal plug. and remove the jack.

8. Lubricate the kingpin, upper bearing and 15. Recheck front end alignment (toe, camber
lower bushing. Position the steering knuckle and caster).
onto the axle eye.

Page 90
 REPAIR INSTRUCTIONS
Reassembly — FA 23 Front Axle 7. Reinstall the brake mechanism, steering
linkage and wheels. Refer to the Steering
1. Check spindle portion of knuckle for wear Component Torque Chart in the rear of this
caused by wheel bearings. Replace if manual and the following additional
necessary. publications:
2. Inspect brake hose and replace if 앫 Air and Brake System Service Manual,
necessary. 16-104
3. Install new bushings using a hydraulic 앫 Wheels, Rims and Tires, 15-101
press, taking care to line up lubrication holes
or grooves with those in the knuckle. 앫 Wheel Bearings Service Manual,
15-701
4. After bushings have been installed, ream to
proper size. Refer to “KNUCKLE DATA 8. Lubricate the kingpin bushings and bearings
CHART — FULL BUSHING TYPE” on page with the recommended grease through the
108 for bushing specifications. Be sure to grease fittings. Refer to “Kingpin Lubrication
remove all metal chips after reaming. Procedures” on page 65.

5. Lubricate bushings, and install the knuckle 9. Remove the axle stands, lower the vehicle
and pin onto the front axle. Tap the bottom and remove the jack.
of the knuckle pin with a soft-faced mallet to 10. Recheck front end alignment (toe, camber
position the pin in the axle center. and caster).
6. Install thrust bearing, taper nut and related
parts. Adjust the knuckle to axle center
clearances.

Page 91
 REPAIR INSTRUCTIONS
Reaming Knuckle Bushings — FA23 The reamers in the sets shown, will finish ream
the bushings to the factory-specified clearance
Front Axles over the standard kingpins. Therefore, it is
imperative that the reamer set be properly
Reamer sets are available for use in obtaining the matched with the front axle shown in the Knuckle
proper clearance between the bushings and Data Charts.
knuckle pin.
After reaming, clean the knuckles and bushings
A typical bushing reamer set such as PT 4375-A thoroughly. Then refer to the proper steering
available from Kent-Moore which consists of the knuckle reassembly procedure.
necessary pilot adapters, reamers, and arbor and
driving assembly. If it is necessary to ream both After lowering the vehicle, check to ensure that
the upper and lower bushings, it is recommended the proper clearances have been obtained. Refer
that one bushing at a time be reamed with the to “STEERING KNUCKLE MEASUREMENTS
proper pilot adapter attached to the opposite end AND ADJUSTMENTS” on page 82.
of the arbor. 59

Figure 59 — Typical Reamer Set

Page 92
 REPAIR INSTRUCTIONS
60 61

Figure 60 — Reamer Assembled for Usage Figure 61 — Reaming Steering Knuckle Bushing

Page 93
 REPAIR INSTRUCTIONS
PITMAN ARM REMOVAL
62

[413]

When removing the pitman arm, it will first be

necessary to remove the drag link. Care should
be taken when removing a taper-style ball socket
from a pitman arm, to not strike the socket with a
hammer without first using some means of
backing-up the pitman arm. Having an assistant
hold a four-pound sledge hammer against the
back of the pitman arm while striking the stud of
the ball socket should be sufficient. Remove the
nut from the ball socket stud, and use a brass
hammer to remove the ball socket.

TRW/TAS Steering Gears

To remove the pitman arm from a TRW/TAS
steering gear, remove the pinch bolt, and then
use a chisel to loosen the pitman arm on the
sector shaft.

Figure 62 — Loosening Pitman Arm Boss

Page 94
 REPAIR INSTRUCTIONS
Sheppard Steering Gears
1. Using a small punch and hammer, bend the
When using a chisel to spread the pitman arm two locking tabs out of the retainer locking
boss in order to loosen or install the pitman slots.
arm, maintain a firm grip on the chisel at all
times. Failure to do this may result in the
chisel flying loose which could cause
personal injury. Never leave the chisel Do not bend the locking tabs into the pitman arm
wedged in the pitman arm boss. If you cannot slot.
remove the pitman arm from the shaft by hand
with a chisel, remove the chisel from the 63

pitman arm and use a puller to remove the

pitman arm. Wear protective eyewear.

Always use new fasteners if the pitman arm pinch

bolts are disturbed.

Figure 63 — Bending Locking Tabs

Page 95
 REPAIR INSTRUCTIONS
2. Coat the face of the locking retainer with 3. Slide the pitman arm puller tool, J 43744,
grease. over the pitman arm and remove the
64
retainer. As the retainer is being removed, it
acts as a jackscrew against the puller to
remove the arm.

The pitman arm will be extremely tight. Do not

pound on the pitman arm or apply any heat.
This can cause damage to the pitman arm or
sector shaft which could result in a failure and
a loss of vehicle control at a later time. Never
weld the pitman arm or sector shaft.
65

Figure 64 — Retainer Coated with Grease

Figure 65 — Removing Pitman Arm

Page 96
 REPAIR INSTRUCTIONS
PITMAN ARM INSTALLATION
[413]
Never apply Never-Seize® to the pitman arm
contact side of the tab lock washer.
TRW/TAS Steering Gears
5. Screw the retainer into the output shaft by
Slide the pitman arm onto the output shaft, hand and align the tabs of the retainer with
making sure to align the timing marks (refer to the notches in the pitman arm.
“Steering Gear Centering” on page 79). Install a 66

new pinch bolt and nut and tighten to:

앫 5/8″ grade 8 bolt — 230–250 lb-ft
(312–339 N폷m).
앫 3/4″ grade 8 bolt — 300–320 lb-ft
(407–434 N폷m).
앫 M16 metric class 10.9 — 200–220 lb-ft
(271–298 N폷m)
앫 M20 metric class 10.9 — 385–405 lb-ft
(522–549 N폷m)

Sheppard M100P Steering Gears

1. Slide the pitman arm onto the output shaft,
making sure the timing marks are aligned
(refer to “Steering Gear Centering” on page
79).
2. If reusing the tab lock retainer, inspect the
assembly for broken tabs or thread damage
before installation. Replace the retainer if
Figure 66 — Locking Tabs Aligned with Pitman Arm
any damage is found. Notches
3. If a new retainer is required, read the
instruction sheet supplied with the retainer 6. Tighten the retainer to the value stamped on
kit. Discard any parts not required for the the retainer.
particular application being serviced.

If a new pitman arm has been installed, the

Three tab lock retainers are supplied with the pitman arm clearance must be measured as
retainer kit, each with differing torque described below. If the original pitman arm has
specifications, 225 lb-ft, 350 lb-ft and 450 lb-ft. been reinstalled, continue with step 10.
The torque value is stamped on the face of each
retainer. Compare the torque value stamped on
the original retainer with the torque value on the
new retainer. Use the retainer with the same
torque value.

4. Apply Never-Sieze® to the threads inside

the output shaft and on the retainer, and on
both sides of the friction washer.

Page 97
 REPAIR INSTRUCTIONS
7. After tightening the retainer to the specified 9. Tighten the retainer to the torque value
torque value, remove the retainer from the stamped on the retainer.
output shaft and measure the distance from
10. After the minimum torque has been reached,
the end of the output shaft (A in Figure 67) to
continue tightening until two of the retaining
the recessed area of the pitman arm (B in
tabs of the tab washer align with the notches
Figure 67).
in the retainer.
앫 Retainer torqued to 225 lb-ft — 3/32″ to 68

5/32″
앫 Retainer torqued to 350 lb-ft — 3/32″ to
5/32″
앫 Retainer torqued to 450 lb-ft — 1/8″ to
3/16″
67

Figure 68 — Aligning Locking Tabs

If the tabs and notches do not align, continue

tightening beyond the specified torque value until
Figure 67 — Measuring Pitman Arm Clearance the tabs do align. Never back off the retainer to
align the tabs. The retainer and pitman arm could
loosen.

If the above measurement does not meet the

acceptable minimum or maximum tolerance,
the pitman arm and output shaft must be
replaced. Failure to take this measurement or
replace worn parts can result in pitman arm
looseness, that could lead to a loss of vehicle
control and severe personal injury.

8. Reinstall the retainer into the output shaft

and hand-tighten. Make sure to align the
tabs of the retainer with the notches in the
pitman arm.

Page 98
 REPAIR INSTRUCTIONS
11. Once the retaining tabs are aligned with the
69

notches, use a punch and hammer to bend

the tabs into the notches.

Always wear safety glasses and never use a

punch that is damaged. Pieces can break off and
hit the eye.

Figure 69 — Bending Locking Tabs

Page 99
 REPAIR INSTRUCTIONS
Sheppard 292, 392, 492 and 592
Steering Gears
If the pitman arm is not installed according to the
Install the pitman arm onto the output shaft, following specifications, the arm could work
making sure the timing marks are in alignment. loose. If this condition is evident, inspect both the
(Refer to “Steering Gear Centering” on page 79.) pitman arm and the output shaft for spline wear. If
either part is worn, replace the necessary parts.
The following chart shows two methods used to Do not weld the pitman arm or output shaft.
retain the pitman arm to the output shaft on Sudden failure could occur.
Sheppard 292, 392, 492 and 592 steering gears.
The chart also provides torque values and
required parts. Use the attachment method and
parts (retainers and washers) as needed, for the
gear being serviced. Use lubricant as specified. 70

Figure 70 — Pitman Arm Installation Chart

Page 100
 REPAIR INSTRUCTIONS
STEERING GEAR REPAIR
Although this manual will enable the trained CRITICAL STEERING SERVICE TIPS!
technician to diagnose a problem in the steering
gear, steering gear overhaul is not covered here. When replacing steering components, no
The various gear manufacturers publish service substitutions should be used. Use exactly the
instructions for their gears that are updated as same model steering gear if replacement is
changes dictate. Whenever steering gear required.
disassembly is necessary, the technician MUST When removing a steering gear, record the
consult the gear manufacturer service manual location of any spacers used in its mounting.
BEFORE work is begun! Reuse these spacers when installing the new
gear.
Pitman arm installation is a critical operation!
Timing marks must be aligned. The various types
NEVER disassemble a steering gear without of retainers must be installed and torqued
first consulting the gear manufacturer service properly. Obtain the manufacturer service manual
literature. Improper gear service can result in for the gear in your chassis, and read it BEFORE
unexpected loss of vehicle control, and doing any steering work!
possible serious injury or death.
Whenever you remove a steering gear, use new
bolts and nuts of the same grade and type as
Steering gear service manuals can be obtained those removed for remounting.
from your local MACK dealer. Dealers can order Any pinch bolts used on the pitman arm should
these manuals by completing a Literature be replaced with new fasteners if they are
Requisition Form, BR313, and faxing or mailing disturbed.
the completed form to the fax number or mailing
address on the BR313 form. Be sure to specify
the steering gear model when placing the order.
Steering Shaft Support Bearing
If additional technical assistance is necessary,
RH Sheppard and TRW Ross provide the A support bearing provides support to the lower
following toll-free hotlines: steering shaft on CL, RD, CV and CT model
chassis. On CL models, the bearing is secured to
앫 RH Sheppard — 800-2RH-SHEP a frame-mounted bracket, whereas on RD, CV
(800-274-7437) and CT models, the bearing is secured to a
steering gear-mounted bracket.
RH Sheppard web site address — 71

www.rhsheppard.com
앫 TRW Ross — 800-879-0899

TRW Ross web site address — www.trw.com

These hotlines may be used to discuss problems

when diagnosing a steering problem. Before
calling either of these hotlines, however, the
Power Steering Troubleshooting Report Form
FO52 must be completed. The steering gear
manufacturer will need this information in order to
provide assistance.

Figure 71 — Support Bearing — CL Models

1. Lower Steering Shaft 3. Center Steering Shaft

2. Support Bearing

Page 101
 REPAIR INSTRUCTIONS
72

Use an accurately calibrated torque wrench to

tighten the bearing mounting bolts by hand. DO
NOT use an air wrench.
73

Figure 72 — Support Bearing — RD, CV and CT Models

1. Lower Steering Shaft 3. Center Steering Shaft

2. Support Bearing

The support bearing must be properly installed

whenever the steering shafts have been removed
and reinstalled. Installation procedures are as Figure 73 — Support Bearing Mounting Bolts
follows:
5. Tighten the Allen set screws in the bearing
CL Models collar to 20 lb-in (2 N폷m).
74

1. Inspect the bearing assembly by rotating the

collar while holding the bearing housing. Any
roughness felt as the bearing is rotated
indicates that the bearing must be replaced.
2. Slide the bearing lower mounting flange onto
the lower steering shaft, followed by the
bearing assembly (collar side down) and the
bearing upper mounting flange.
3. Position the lower steering shaft in the
opening of the bearing mounting bracket,
and then slide the bearing assembly and
mounting flanges against the underside of
the bearing mounting bracket.
4. Install the bearing mounting bolts and
tighten to 30 lb-ft (41 N폷m).

Figure 74 — Bearing Collar Set Screws

Page 102
 REPAIR INSTRUCTIONS
RD, CV and CT Models 4. Lift the rubber boot to access the Allen set
screws in the bearing collar, and then tighten
1. Inspect the bearing assembly by rotating the
the screws to 20 lb-in (2 N폷m).
collar while holding the bearing housing. Any
roughness felt as the bearing is rotated
indicates that the bearing must be replaced.
2. Slide the bearing onto the lower shaft. On CT models, the support bearing collar does
not contain set screws.
76

If the bearing does not slide onto the shaft easily,

check the shaft splines for rust or burrs. Clean the
shaft and/or remove any burrs as required. If the
bearing still does not slide onto the shaft easily,
replace the bearing.

3. Install the bearing mounting bolts. Draw the

bearing assembly down onto the mounting
bracket evenly by alternately tightening the
mounting bolts until reaching the final torque
specification of 30 lb-ft (41 N폷m).
75

Figure 76 — Support Bearing Set Screws

Figure 75 — Support Bearing Mounting Bolts

Use an accurately calibrated torque wrench to

tighten the bearing mounting bolts by hand. DO
NOT use an air wrench.

Page 103
 REPAIR INSTRUCTIONS
STEERING GEOMETRY CHECKSHEET
77

Figure 77 — Steering Geometry Checklist

Page 104
 REPAIR INSTRUCTIONS
78

Figure 78 — Steering Geometry Checklist (continued)

Page 105
 NOTES

Page 106
SPECIFICATIONS

SPECIFICATIONS

Page 107
 SPECIFICATIONS
FRONT AXLE AND STEERING SPECIFICATIONS
KNUCKLE DATA CHART — FULL BUSHING TYPE
Pin-to-Bushing
Knuckle Pin Size Bushing I.D. Clearance
Upper Lower Kent-Moore Reamer
Axle Model Upper Lower Ream Ream Min. Max. Tool No.
FA23 1.7470 2.0980 1.7485 2.0995 0.0005 0.0020 J 26483-01
1.7465 1.0975 1.7475 2.0985

KNUCKLE DATA CHART — UPPER NEEDLE BEARING AND PRESIZED LOWER BUSHING — NO REAMING REQUIRED
Knuckle Pin Size Pin-to-Bushing Clearance
Axle Models Upper Lower Bushing I.D. Installed Min. Max.
FAW12, 14.3, 16, 18, 20 1.3755 1.6255 1.6330 0.0010 0.015
1.3750 1.6250 1.6265

Page 108
 SPECIFICATIONS
FRONT AXLE SPECIFICATIONS adjustable, and are listed for informational
purposes only. Also, kingpin inclination is not
The following specifications cover current adjustable and if not within specifications,
production MACK front axle information including replacement of parts is indicated. Refer to other
unit symbol, rating, pivot center, dimensions and manufacturer’s service manuals for additional
knuckle pin inclination. Specifications listed are information concerning vendor axles.
given for an empty vehicle. Pivot centers are not

Pivot
Axle Rating Center
Pounds Suspension Type Inches Spindle Diameter
Unit Symbol (Kg) Ground Load* (mm) Kingpin Inclination Inches (mm)
FAW12 12,000 12,000 lb. std. 70.06 Before 7/1/81 Inner Bearing —
(5 400) 12,000 lb. opt. H.D. (1779.6) 7°0′ + 0′−15′ 2.620 (66.7)
10,500 lb. opt. Taperleaf After 7/1/81 Outer Bearing — 1.75
Multileaf (44.4)
7°30′ + 0′−15′
FAW14.3 14,300 14,300 lb. std.
(6 500) 12,000 lb. opt. Taperleaf
Multileaf
FAW16 16,000 16,000 lb. std. Taperleaf FA 65.50 Before 3/1/82 Inner Bearing — 3.00
(7 300) (1663.7) 5°30′ + 30′−30′ (76.2)
FAW 69.88 After 3/1/82 Outer Bearing — 2.25
FA(W)18 18,000 18,000 lb. std. (1774.8) (57.1)
(8 200) 18,000 lb. opt. H.D. 6° + 30′−30′
16,000 lb. opt.
14,000 lb. opt.
Taperleaf Multileaf
FA(W)20 20,000 20,000 lb. std
(9 100) 20,000 lb. opt. H.D.
18,000 lb. opt.
16,000 lb. opt.
14,000 lb. opt.
Taperleaf Multileaf
FA23 23,000 23,000 lb. std. 77.88 3° 30′ + 0′−30′ Inner Bearing — 3.37
(10 400) 20,000 lb. opt. (1978.0) (85.7)
Multileaf Outer Bearing — 2.12
(54.0)

*When spring ground load rating exceeds axle rating, spring is certified to axle rating.

Page 109
 SPECIFICATIONS
TORQUE REQUIREMENTS AND Steering Shaft Universal Joint Pinch
PROCEDURES Bolts

Do not reuse steering shaft or steering lever Check steering shaft pinch bolt torque at each C
clamp bolts. The following torque values are for and D inspection interval. Replace any bolts that
grade 8 bolts without lubrication. Any type of are corroded.
lubricants, including such compounds as sealers
and rust preventatives, must be removed from
the threads of the bolts and nuts before they are The torque requirements for steering shaft
tightened. universal joint grade 8 pinch bolts installed with
nylon collar type locknuts are as follows:

This section lists recommended torques for Bolt Size Torque

various parts of the steering system. Always 3/8″-8 UNF Grade 8 45–50 lb-ft (61–68 N폷m)
make sure that specified fasteners are used.
7/16″-8 UNF Grade 8 65–75 lb-ft (88–102 N폷m)

Steering Wheel Retaining Nut Pitman Arm Retention

The timing mark on the pitman arm and the
stamped mark on the steering gear output shaft
Aftermarket steering wheels MUST NOT be are to be carefully aligned before the retaining
installed on vehicles equipped with the MACK device is tightened.
RSA (Bendix® ABS-6 Advanced with ESP®).
Only OEM-supplied replacement steering wheels Where the pitman arm is secured by a pinch bolt,
should be used. During any service procedure the following torques apply:
that involves reinstallation or replacement of the
OEM steering wheel, use care not to crush or Bolt Size Torque
damage the steering angle sensor. 5/8″-18 Grade 8 230–250 lb-ft
(312–339 N폷m)
3/4″-16 Grade 8 300–320 lb-ft
The steering wheel should be centered to a (407–434 N폷m)
tolerance of ±5 degrees with the front wheels in M16 x 2 Grade 10.9 200–220 lb-ft
the straight-ahead position before the steering (270–300 N폷m)
wheel retaining nut is tightened. Tighten the M20 x 2.5 Grade 10.9 385–405 lb-ft
steering wheel retaining nut to the following (520–550 N폷m)
specifications:

7/8″-20 UNEF 45–55 lb-ft (61–75 N폷m)

Steering Shaft Bearing Set Screws Pitman arm pinch bolts or nuts are not to be
reused.
The set screws used on the steering shaft
support bearings are to be tightened to the
following specifications:

#10-32 UNF 18–22 lb-in (2.0–2.5 N폷m)

1/4″-28 UNF 18–22 lb-in (2.0–2.5 N폷m)

Page 110
 SPECIFICATIONS
On Sheppard steering gears with output shafts 5. Bend the two opposing tabs on the locking
having a serrated taper and threaded retaining washer into the notches in the retainer/bolt.
nut on the shaft end, torque the nut as follows,
using white lead between the arm and the nut:
Drag Link to Pitman Arm Pinch Bolt
Thread Torque
1-3/8″-12 410–460 lb-ft On models where the drag link is secured to the
(556–624 N폷m) pitman arm by a pinch bolt, the torque
1-1/2″-12 450–500 lb-ft requirements are as follows:
(610–678 N폷m)
1-3/4″-12 500–550 lb-ft Bolt Size Torque
(678–746 N폷m) 5/8″-18 Grade 8 230–250 lb-ft
(312–339 N폷m)
On Sheppard steering gears with a one-piece M16 x 2 Grade 10.9 200–220 lb-ft
retainer/bolt assembly and a washer, the (270–300 N폷m)
retainer/bolt shoulder, thread and washer should
be coated with Never-Sieze®, or equivalent. The
retainer/bolt assembly is the installation tool as
Drag Link, Steering Cross Tube and
well as the retention device. Do not remove them Booster Cylinder Clamp Pinch Bolts
after installing the pitman arm and torquing to the
following values (HAND TORQUE ONLY! DO The pinch bolt on the drag link, cross steering
NOT USE IMPACT.): tube and the booster cylinder adjustable ball
Bolt Size Torque socket clamp is to be tightened to the following
specification:
5/8″-18 UNF 225–275 lb-ft
(305–373 N폷m)
Bolt Size Torque
3/4″-16 UNF 450–500 lb-ft
(610–678 N폷m) 5/8″-11 UNC 50–60 lb-ft (68–81 N폷m)
1/2″-13 UNC 42–50 lb-ft (57–68 N폷m)
On Sheppard steering gears with a one-piece M16 x 2 50–60 lb-ft (68–81 N폷m)
retainer/bolt assembly, friction washer and
washer with locking tabs, the following procedure Drag Link Ball Socket Stud Nut
applies:
1. The retainer/bolt shoulder and thread, The drag link ball socket stud should be firmly
friction washer and locking washer should seated into the female taper of the drag link
be coated with Never-Sieze®, or equivalent. before torque is applied to the stud nut. Nut
2. Install the retainer/bolt and locking washer should be tightened to minimum torque as listed
assembly, aligning the two flat tabs of the below:
locking washer with the slots in the pitman
arm. Thread Size Torque
7/8″-14 UNC 238–264 lb-ft
3. Torque the retainer bolt to: (323–358 N폷m)
M20 x 1.5 145–155 lb-ft
Bolt Size Torque (196–210 N폷m)
5/8″-18 UNF 350 lb-ft (475 N폷m)
3/4″-16 UNF 450 lb-ft (610 N폷m)

4. Upon reaching the low end of the specified

torque, continue advancing the retainer/bolt
until the notches in the retainer/bolt are
aligned with the next tab on the locking
washer. (HAND TORQUE ONLY! DO NOT
USE IMPACT.)

Page 111
 SPECIFICATIONS
Steering Gear Mounting Bolts On Sheppard 492S and 592S steering gears with
threaded mounting holes (SAE threads), or on
The use of Loctite® or similar thread locking installations having a steering gear mounting
compounds is not permitted for use on the adapter bracket with threaded mounting holes
steering gear mounting bolts. Additionally, the (SAE threads), the following torque specifications
use of oil, grease or other lubricants is not apply for installation of grade 8 patchlock bolts.
permitted.
Thread Size Torque
9/16″-18 UNF 170–200 lb-ft
(230–270 N폷m)
DO NOT reuse steering gear mounting bolts or 5/8″-18 UNF 185–215 lb-ft
nuts. The fasteners MUST be replaced with new (250–290 N폷m)
parts and tightened to proper specifications.
On Sheppard 492S and 592S steering gears with
threaded mounting holes (SAE threads), or on
Steering gear mounting bolts and/or nuts must be installations having a steering gear mounting
tightened to the specifications as outlined below. adapter bracket with threaded mounting holes
(SAE threads), the following torque specifications
On TRW and Sheppard steering gears where the apply for installation of grade 5 patchlock bolts.
steering gear housing is threaded (SAE threads),
the following torque specifications apply for Thread Size Torque
installation of grade 8 patchlock bolts.
9/16″-18 UNF 120–150 lb-ft
(163–203 N폷m)
Thread Size Torque
5/8″-18 UNF 170–200 lb-ft
1/2″-20 UNF 90–100 lb-ft (122–136 N폷m) (240–270 N폷m)
3/4″-16 UNF 300–330 lb-ft
(407–447 N폷m)
Power Steering Pump Gear
7/8″-14 UNC 450–500 lb-ft
(610–678 N폷m) Retaining Nut

On Sheppard and TRW steering gears where the The gear retaining nut for power steering pumps
gear housing is threaded (metric threads), the used on MACK MP7 and MP8 engines must be
following torque specifications apply for tightened to the following specification:
installation of metric class 10.9 patchlock bolts.
Thread Size Torque
Thread Size Torque 3/4″-16 UNF 66–80 lb-ft (90–110 N폷m)
M16 x 2 219–243 lb-ft
(297–329 N폷m)
Hose Fittings (SAE O-Ring Boss
M20 x 2.5 428–473 lb-ft
(580–641 N폷m) Fittings)
M24 x 3 550–600 lb-ft
(814–829 N폷m) When installing SAE O-ring boss-type hose end
fittings into power steering pumps having
aluminum bodies, tighten the fittings to the
specifications as follows:

Thread Size Torque

3/4″-16 30–37 lb-ft (40–50 N폷m)
1-1/6″-12 44–59 lb-ft (60–80 N폷m)

Refer to the “STEERING COMPONENT

TORQUE CHART” section.

Page 112
 SPECIFICATIONS
STEERING COMPONENT TORQUE CHART
79

Figure 79 — Steering Component Torque Chart

Page 113
 NOTES

Page 114
SPECIAL TOOLS & EQUIPMENT

SPECIAL TOOLS & EQUIPMENT

Page 115
 SPECIAL TOOLS & EQUIPMENT
SPECIAL TOOLS

Special Tools for Front Axle and

Steering Repairs and Testing

Tool No. Description

J 5421-02 Thermometer
J 23775-01 100–600 lb-ft Torque Wrench
J 24407 30–250 lb-ft Torque Wrench
J 26487-C Power Steering Analyzer
J 26900-8 Thickness Gauge
J 28593 Power Steering Analyzer Adapter Package
J 29048 Tapered Thickness Gauge
J 43744 Sheppard Steering Gear Puller
J 44004 Kingpin Cap Tool Kit
J 7872 Dial Indicator Set (Includes Magnetic Base)
PT 4375-A Kingpin Bushing Service Kit
6990-O21407X1 Poppet Valve Adjusting Screw/Tool for TRW Steering Gears (Available through the
MACK Parts System)
8148-3331812K Steering Gear Internal Pressure Relief Valve Test Plug, Sheppard Steering Gears
(Available through the MACK Parts System)
J 37130 Steering Gear Internal Pressure Relief Valve Test Plug, TRW Steering Gears (Available
through the MACK Parts System)

Unless otherwise noted, the above tools are

available from:

SPX SERVICE SOLUTIONS

28635 MOUND ROAD

WARREN, MICHIGAN 48092-3499

TEL: 1-800-328-6657

FAX: 1-800-578-7375

WEBSITE: www.servicesolutions.spx.com

Page 116
INDEX

INDEX

Page 117
 INDEX
A K
ABOUT THIS MANUAL . . . . . . . . . . . . . . . . . . .6 KINGPIN LATERAL PLAY (FAW 12, 14.3, 16,
ADVISORY LABELS . . . . . . . . . . . . . . . . . . . . .2 18[W], AND 20[W] AXLES) . . . . . . . . . . . . 82
AXLE CENTER SECTION . . . . . . . . . . . . . . . .71 KINGPIN LUBRICATION PROCEDURES . . . 65
AXLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 KNUCKLE STOP BOLT ADJUSTMENT
(TURNING CIRCLE) . . . . . . . . . . . . . . . . . 72
D
P
DISASSEMBLY — FA 23 FRONT AXLES . . .89
DISASSEMBLY — FAW 12, 14.3, 16, 18(W) PITMAN ARM INSTALLATION . . . . . . . . . . . . 97
AND 20(W) FRONT AXLES . . . . . . . . . . . .87 PITMAN ARM REMOVAL . . . . . . . . . . . . . . . . 94
DRAG LINK BALL SOCKET STUD NUT . . . .111 PITMAN ARM RETENTION . . . . . . . . . . . . . 110
DRAG LINK TO PITMAN ARM PINCH PIVOT CENTERS . . . . . . . . . . . . . . . . . . . . . . 10
BOLT . . . . . . . . . . . . . . . . . . . . . . . . . . . .111 POWER STEERING GEAR INTERNAL
DRAG LINK, STEERING CROSS TUBE AND LEAKAGE FLOW TEST . . . . . . . . . . . . . . 48
BOOSTER CYLINDER CLAMP PINCH POWER STEERING HOSES . . . . . . . . . . . . . 65
BOLTS . . . . . . . . . . . . . . . . . . . . . . . . . . .111 POWER STEERING PUMP GEAR
RETAINING NUT . . . . . . . . . . . . . . . . . . 112
E POWER STEERING PUMP MODEL
EXPLANATION OF NUMERICAL CODE . . . . .5 CODES . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
POWER STEERING PUMP PERFORMANCE
F TEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
POWER STEERING SYSTEM HYDRAULIC
FLUID FOAMING CHECK . . . . . . . . . . . . . . . .44 TESTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
FRAME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71 PRELIMINARY CHECKS . . . . . . . . . . . . . . . . 22
FRONT AXLE AND STEERING
ADJUSTMENTS . . . . . . . . . . . . . . . . . . . .72 R
FRONT AXLE AND STEERING
IDENTIFICATION . . . . . . . . . . . . . . . . . . .10 REAMING KNUCKLE BUSHINGS — FA23
FRONT AXLE AND STEERING FRONT AXLES . . . . . . . . . . . . . . . . . . . . . 92
INTRODUCTION . . . . . . . . . . . . . . . . . . . .16 REASSEMBLY — FA 23 FRONT AXLE . . . . . 91
FRONT AXLE AND STEERING REASSEMBLY — FAW 12, 14.3, 16, 18(W)
SPECIFICATIONS . . . . . . . . . . . . . . . . . .108 AND 20(W) FRONT AXLES . . . . . . . . . . . 90
FRONT AXLE AND STEERING RIDE/HANDLING/STEERING EVALUATION
TROUBLESHOOTING . . . . . . . . . . . . . . . .22 WORKSHEET . . . . . . . . . . . . . . . . . . . . . . 60
FRONT AXLE SPECIFICATIONS . . . . . . . . .109
S
FRONT END ALIGNMENT . . . . . . . . . . . . . . .71
SAFETY INFORMATION . . . . . . . . . . . . . . . . . 2
G SERVICE PROCEDURES AND TOOL
GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . .18 USAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SHEPPARD 292, 392, 492 AND 592
H STEERING GEARS . . . . . . . . . . . . . . . . 100
SHEPPARD M100P STEERING GEARS . . . . 97
HOSE FITTINGS (SAE O-RING BOSS SHEPPARD POWER STEERING GEAR
FITTINGS) . . . . . . . . . . . . . . . . . . . . . . . .112 RELIEF POPPET ADJUSTMENT
HYDRAULIC TESTS . . . . . . . . . . . . . . . . . . . .22 (AUTOMATIC-TYPE) . . . . . . . . . . . . . . . . 75
SHEPPARD POWER STEERING GEAR
I RELIEF POPPET ADJUSTMENT
IDENTIFY THE COMPLAINT . . . . . . . . . . . . .51 (MANUAL-TYPE) . . . . . . . . . . . . . . . . . . . 74
INSPECTIONS AND MEASUREMENTS SHEPPARD STEERING GEARS . . . . . . . . . . 95
CHART . . . . . . . . . . . . . . . . . . . . . . . . . . .51 SPECIAL TOOLS . . . . . . . . . . . . . . . . . . . . . 116
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . .51

Page 118
 INDEX
SPECIAL TOOLS FOR FRONT AXLE AND STEERING MAINTENANCE . . . . . . . . . . . . . . 62
STEERING REPAIRS AND TESTING . . .116 STEERING SHAFT BEARING SET
SPRINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68 SCREWS . . . . . . . . . . . . . . . . . . . . . . . . . 110
STEERING (TURNING) ANGLE AND STEERING SHAFT SUPPORT BEARING . . 101
TURNING RADIUS . . . . . . . . . . . . . . . . . .68 STEERING SHAFT UNIVERSAL JOINT
STEERING COMPONENT TORQUE PINCH BOLTS . . . . . . . . . . . . . . . . . . . . . 110
CHART . . . . . . . . . . . . . . . . . . . . . . . . . . .113 STEERING SYSTEM GENERAL
STEERING COMPONENTS . . . . . . . . . . . . . .18 INSPECTIONS . . . . . . . . . . . . . . . . . . . . . 68
STEERING GEAR ADJUSTMENTS . . . . . . . .77 STEERING SYSTEM MAINTENANCE . . . . . . 62
STEERING GEAR ADJUSTMENTS STEERING SYSTEMS . . . . . . . . . . . . . . . . . . 10
CHART . . . . . . . . . . . . . . . . . . . . . . . . . . . .78 STEERING WHEEL RETAINING NUT . . . . . 110
STEERING GEAR AND PUMP FLOW
REQUIREMENTS . . . . . . . . . . . . . . . . . . .43 T
STEERING GEAR BLEED PROCEDURES . .63
STEERING GEAR CENTERING . . . . . . . . . . .79 TORQUE REQUIREMENTS AND
STEERING GEAR MOUNTING BOLTS . . . .112 PROCEDURES . . . . . . . . . . . . . . . . . . . . 110
STEERING GEAR RELIEF POPPET TROUBLESHOOTING CHARTS . . . . . . . . . . 23
ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . .73 TROUBLESHOOTING TERMS . . . . . . . . . . . . 19
STEERING GEAR REPAIR . . . . . . . . . . . . . .101 TRW/TAS SERIES POWER STEERING
STEERING GEOMETRY CHECKSHEET . . .104 GEAR RELIEF POPPET
STEERING KNUCKLE . . . . . . . . . . . . . . . . . .71 ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . 73
STEERING KNUCKLE BEARING TRW/TAS STEERING GEARS . . . . . . . . . 94, 97
ADJUSTMENT (FA 23 AXLES) . . . . . . . . .86
STEERING KNUCKLE MEASUREMENTS V
AND ADJUSTMENTS . . . . . . . . . . . . . . . .82
STEERING KNUCKLE OVERHAUL . . . . . . . .87 VEHICLE INSPECTIONS AND
STEERING KNUCKLE VERTICAL MEASUREMENTS FOR SHIMMY AND
CLEARANCE (FAW 12, 14.3, 16, 18[W], RESONANT RIDE . . . . . . . . . . . . . . . . . . . 51
AND 20[W] AXLES) . . . . . . . . . . . . . . . . . .84 VEHICLE INSPECTIONS AND
STEERING LINKAGE (CROSS STEERING MEASUREMENTS PROCEDURES . . . . . 53
TUBE, DRAG LINK AND STEERING
LEVERS) . . . . . . . . . . . . . . . . . . . . . . . . . .69

Page 119
 NOTES

Page 120
 MACK FA(W)
FRONT AXLE
AND STEERING
SYSTEM
SERVICE MANUAL

PRINTED IN U.S.A.
12-101 © MACK TRUCKS, INC. 2006