Chapter 6 CLUTCHES

1. Advantages and Disadvantages of Clutches by Type of Drive System6-1

2. Principal Differences Between Dry-Type and Wet-Type Clutches ..... 6-2
3. Structure and Functions of Clutch ........................................................ 6-3
3.1 Power Clutch ........................................................................................................... 6-4
3.2 Flow Divider (Wet-Type Clutch)............................................................................... 6-6
3.3 Clutch Master Cylinder (Dry-Type Clutch)............................................................... 6-6
3.4 Hydraulic Booster (Wet-Type Clutch) ...................................................................... 6-7
3.5 Clutch Release Cylinder .......................................................................................... 6-8
3.6 Pressure Plate Assembly ...................................................................................... 6-17
3.7 Clutch Master Cylinder (Dry-Type Clutch)............................................................. 6-21
3.8 Clutch Release Cylinder ........................................................................................ 6-23
4. Adjustment ............................................................................................ 6-25
4.1 Bleeding Clutch Hydraulic System ........................................................................ 6-25
4.2 Clutch Pedal Adjustment (Dry-Type) ..................................................................... 6-26
4.3 Clutch Pedal Adjustment (Wet-tType) ................................................................... 6-27
4.4 Checking Clutch Disc for Wear.............................................................................. 6-28
5. Troubleshooting.................................................................................... 6-29
6. Service Data........................................................................................... 6-31
6
6.1 Dry-Type Clutch..................................................................................................... 6-31
6.2 Wet-Type Clutch.................................................................................................... 6-35
 CLUTCHES

1. Advantages and Disadvantages of Clutches by Type of Drive System

Chapter 6 CLUTCHES

Type Structure Advantage/Disadvantage

Most popular type of clutches. As half clutching
makes delicate loading and unloading opera-
tions possible, this type of clutch is favored
by veteran fork truck operators who do not
like torque converter drive trucks. This clutch
contributes to the fuel economy because it
Dry-type clutch

allows economical use of engine output with

limited power transmission loss.
Depending on the nature of loading/unloading
operation, excessive half clutching shortens
the service life of clutch disc and increases
maintenance cost. A truck with this type of
clutch is harder to operate than a torque con-
verter vehicle and requires a certain degree
Direct drive

213544
of skill to operate.
Although this type of clutch is equal to the dry
type in pedal operation, feeling and contribu-
tion to fuel economy, it markedly longer in
clutch disc service life even during frequent
half clutching.
Wet-type clutch

On trucks used during long periods under

severe conditions and those provided with
attachments like roll clamp that are operated
with frequent half clutching or equipped with
a hinged fork that requires traction force, this
type of clutch lasts longer so that it is eco-
nomically more advantageous than its dry-
type counterpart.
213545

This torque converter is so easy to operate that

it contributes to high operation efficiency with
limited operator fatigue. (Depending on the
nature of operation, a torque converter drive
truck is approximately 10% higher in effi-
ciency than its direct drive counterpart.)
Hydraulically operated wet-type clutch incorpo-
rated in the transmission last longer, offering
Torque converter
Powershift drive

the same advantage as that of wet-type

clutch (direct drive) trucks mentioned above.
In fuel consumption versus work load, a torque
converter truck is inferior to its direct drive
counterpart by about 10% due to power
transmission loss. (Actually, fuel consumption
per hour is about 20% more, while work load
213546 for the corresponding length of time is greater
by about 10%. This is for reference only
because these percentages differ, depending
on the nature of operation.)

6-1
CLUTCHES

2. Principal Differences Between Dry-Type and Wet-Type Clutches

Pressure plate Clutch disc Input shaft Clutch housing

Engine S4Q2 S4S
K15
mounted K21 K25
Identification
Yellow Blue Black
mark
Dry-type

12 12 8
Spring
pieces pieces pieces

Identification
mark 213548 213551

213547

Engine S4S S4Q2

Wet-type

mounted K25 K21, K15

Identification
Brown Pink
mark

12
Spring 10 pieces 213550
pieces 213549 213552

Clutch pedal Clutch shifter shaft Release bearing E/G packing

Grease lubricated type
Not provided
Dry-type: With grease nipple
L=40.7mm
Dry-type

213554 213557

Provided

L
Wet-type

Wet-type:
L=40.7mm Without grease nipple

213553 213556
213555 213558

6-2
 CLUTCHES

3. Structure and Functions of Clutch

5
8

213559

1 Clutch disc 6 Clutch shifter shaft

2 Pressure plate assembly 7 Shifter case
3 Input shaft 8 Stopper ring
4 Clutch shifter 9 Clutch fork
5 Release bearing

The dry-type clutch has an opening at the top of the The wet-type clutch uses a closed cover because of its
housing for replacement of the clutch disc. For ease of construction that cools the clutch disc with return oil
clutch disc replacement, the input shaft is split from the from the clutch booster. Cooled oil returns to the
input gear so that it is allowed to slide by spline toward hydraulic tank by centrifugal force created by the rota-
the transmission side. tion of flywheel. The oil also serves as hydraulic fluid.
The pressure plate assembly is common in size to 1 The pressure plate assembly is common in size to 1
ton through 3 ton class trucks with only difference in ton through 3 ton class trucks with only difference in
the number of pressure springs the number of pressure springs.

6-3
CLUTCHES

3.1 Power Clutch

3.1.1 Dry-type Clutch

6 1

213560

1 Bracket 4 Clutch master cylinder

2 Clutch pedal 5 Clutch release cylinder
3 Reservoir tank 6 Stopper bolt

The dry-type clutch has the clutch pedal directly pin The clutch release cylinder automatically compen-
connected to the push rod of the clutch master cylin- sates for changes in the position of the release levers
der. of the pressure plate assembly due to clutch disc wear.
Because of this feature, there is no need for further
pedal adjustment once the pedal is properly adjusted
at the time of assembly.

6-4
 CLUTCHES

3.1.2 Wet-type Clutch

3
2
7 1

213561

1 Bracket 5 Hydraulic booster

2 Clutch pedal 6 Clutch release cylinder
3 Flow divider 7 Stopper bolt
4 Reservoir tank

The wet-type clutch has the hydraulic booster installed The clutch release cylinder automatically compen-
behind the clutch pedal. sates for changes in the position of the release levers
of the pressure plate assembly due to clutch disc wear.
Because of this feature, there is no need for further
pedal adjustment once the pedal is properly adjusted
at the time of assembly.

6-5
CLUTCHES

3.2 Flow Divider (Wet-Type Clutch)

1 Flow divider
2 Elbow and nut assembly 3,5
3 Elbow and nut assembly
4 Elbow and nut assembly
5 O-ring
A flow divider valve is a form of pressure-compen-
sated flow control valve which received one input flow
1
from hydraulic pump and splits it into two output flows;
to the hydraulic booster and to the steering valve.
2,5 4,5
213562
3.3 Clutch Master Cylinder (Dry-Type Clutch)

1 2 6

5 3
4

213563

1 Body 4 Push rod

2 Piston assembly 5 Boot
3 Snap ring 6 Filler union

6-6
 CLUTCHES

3.4 Hydraulic Booster (Wet-Type Clutch)

2 4 6 1

3 5

213564
1 Booster body 4 Filler assembly
2 Master cylinder assembly 5 Wire clip assembly
3 Bolt, Spring washer 6 Booster piston assembly
A hydraulic booster converts the pedal force applied to
a clutch pedal to hydraulic pressure and sends the
hydraulic pressure to the clutch release cylinder. The
hydraulic booster serves as a function of the clutch
master cylinder in a dry-type clutch.
Also it utilizes the hydraulic fluid pressure from the flow
divider valve to reduce the force required to press the
clutch pedal.

6-7
CLUTCHES

3.5 Clutch Release Cylinder

2 1

5 4 6

3 7

213565

1 Body 5 Yoke
2 Piston assembly 6 Boot
3 Spring 7 Air bleeder valve
4 Release rod

6-8
 CLUTCHES

3.5.1 Disassembly
The input shaft of the manual transmission is a type For removal of clutch shaft, however, the engine and
that can be split from the internal gearing. transmission assembly needs to be dismounted from
This enables the pressure plate assembly, clutch disc, the truck.
release bearing, etc. to be removed and installed, with (With the engine and transmission assembly mounted
the transmission assembly installed to the truck body. on the truck, there is no room for pulling out the clutch
shaft.)

2
6
1

213566
Disassembly sequence
1 Hose (wet-type clutch only) 4 Clutch disc
2 Clutch cover 5 Pressure plate assembly
3 Clutch release cylinder pin 6 Release bearing, clutch shifter

6-9
CLUTCHES

Suggestions for Disassembly

(1) Holding pressure springs
Depress the clutch pedal, and turn in two bolts
(special tools for removal/installation of the pres-
sure plate) to compress the springs.

Special tool needed

M10×1.5 40
Bolt F1145-10050
Washer 92301-02700
50
Unit:mm 213567

(2) Remove the stopper ring from input shaft.

Stopper ring
The stopper ring can be easily removed by slightly
pulling out the input shaft to the flywheel side.

215207

(3) Sliding input shaft into transmission

The input shaft is held in position by steel ball so
that it takes effort to move at first.

213568

6-10
 CLUTCHES

(4) Clutch shifter shaft, Raise

Loosen the air bleeder valve of the clutch release Dry-type clutch
cylinder to relieve oil pressure, and remove the
pin connecting the clutch release cylinder. Then,
lift up the clutch shifter shaft avoiding the clevis of
the release cylinder rod.

Clutch shifter shaft

213569

Wet-type clutch

Clutch shifter shaft

213570

(5) Removing clutch disc and

pressure plate assembly
Position the dowel pins as shown.
(6) Replacing input shaft
When removing the input shaft for replacement,
dismount the engine and transmission assembly
from the truck.

45°approx.
Dowel pin

213571

6-11
CLUTCHES

3.5.2 Inspection and Repair

(1) Clutch disc

(a)Facing thickness

A: Standard value B: Repair or service limit

Item Dry-type
A Both sides: 9.2±0.3 mm
Facing thickness Each side: 2.3 mm
B
Both sides: 5.5 mm

Replace the clutch disc if wear exceeds the service 213572

limit.
Note:If the facings are badly worn beyond the service
limit, the release cylinder is no longer effective in
compensating for facing wear, causing the clutch
to slip. In this case, replace the clutch disc imme-
diately.
(b)Inspection of facings
Check the clutch disc for broken or fatigued tor-
sion springs and loose rivets. Also check for
hardened friction surfaces and oil or grease on
the surfaces. Replace the clutch disc if defec-
tive.

213573

(c)Disc face runout

A: Standard value
Disc runout (at rim) A 1.0 mm maximum

If the disc runout exceeds the standard value, replace

the disc.

213574
(d)Others
Check for hub spline wear, worn damper and
scratches on the friction surfaces.
Replace any part found to be defective.

6-12
 CLUTCHES

(2) Pressure plate assembly

(a)Check the friction surface of the pressure plate
for burns and groove marks.
(b)Check the friction surface of the pressure plate
for distortion.
Note:For the procedures for disassembling and reas-
sembling the pressure plate assembly, refer to
“Disassembly and Reassembly of Pressure Plate
Assembly.”

213575

(3) Release bearing

(a)Check the release bearing for smoothness of
rotation, with the bearing mounted on the
shifter.
(b)Replace the bearing if it spins rough, makes
abnormal noises or its end face in contact with
the release levers is badly worn.

213576

(4) Shifter
Check the fork groove for wear. See if the shifter
slides smoothly without any sign of binding.

Clutch fork groove for wear

215112

(5) Input shaft

(a)Check for ridged splines.
(6) Flywheel and pilot bearing
(a)Check the friction surface of the flywheel for
burns and groove marks.
(b)Check the pilot bearing for wear.
(7) Other parts
(a)Check the clutch fork and clutch shifter shaft for
bend and/or runout.
(b)Check the needle roller bearing for damage.
213577
A: Standard value B: Service limit
Release fork, A 0.05 mm
clutch shifter shaft run out B 0.1 mm

6-13
CLUTCHES

3.5.3 Reassembly

4 6

1 3

213578
Reassembly sequence
1 Release bearing, clutch shifter 4 Bolts, Washers (special tools)
2 Clutch disc 5 Clutch shifter shaft
3 Pressure plate assembly 6 Cover

Suggestions for Reassembly

(1) Applying grease to sliding faces
Apply a small amount of molybdenum disulfide
grease (Never-Seez or equivalent) to the surfaces
shown by arrow marks.

213579

6-14
 CLUTCHES

(2) Installing pressure plate assembly

(a)Identifying by identification mark (Gasoline
M10×15 40
engine, dry-type clutch)

Item Dry-type Wet-type 50

Unit:mm
Engine S4Q2 S4S S4S S4Q2
mounted K21 K25 K25 K21
Identification
Yellow Blue Brown Pink
mark
Spring 12 pieces 12 pieces 12 pieces 10 pieces
Identification mark
(b)Using bolts (for removal and installation of pres- 213580
sure plate), compress the pressure springs and
install the pressure plate assembly into place in
the clutch housing.

Special tool needed

Bolt F1145-10050
Washer 92301-02700

(3) Installing clutch disc assembly

(a)Push in the input shaft in order for it to protrude
to the position indicated by the dotted line
beforehand.

213581

(b)Suspend the clutch disc on a wire or install the

facing in the correct direction, and align its hub
to the input shaft. Then, insert the input shaft
into the hub of the clutch disc.
Transmission Engine side
side

213582

(c)Back off the input shaft until its stopper ring con-
tacts the input gear. The locking ball goes into
the groove of input gear and the input shaft will
be set in position. Stopper ring

213583

6-15
CLUTCHES

(4) Securing pressure plate assembly

Tighten the mounting bolts to the specified torque,
and remove the bolts and washers (special tools
for compressing the pressure springs).

A: Standard Value
Plate mounting bolt
A 17 N·m
tightening torque

213584

(5) Adjusting release lever height

Press the clutch gauge (for adjusting release lever
Clutch gauge
clearance) against the side of the clutch cover.
Watching the clearance between the release lever
and the gauge, adjust the lever height.

Special tool needed

Clutch gauge 91268-02200

26.5 mm

213585

6-16
 CLUTCHES

3.6 Pressure Plate Assembly

3.6.1 Disassembly

8
6
4
5

3 213586
Disassembly sequence
1 Lock plate 6 Return spring
2 Lever nut 7 Split Pin, Washer, Pin
3 Bolt 8 Release lever, Lever support assembly, Pin
4 Clutch cover 9 Pressure plate
5 Pressure spring

6-17
CLUTCHES

Suggestions for Disassembly

(1) Provide a matching mark across the clutch cover
and pressure plate beforehand.

213587

(2) Using bolts, washers and nuts as special tools (for

disassembling pressure plate), gradually loosen 40
the clutch springs. M10×1.5

Special tool needed 5

10
Bolt 91268-01900 Unit:mm
Washer 92301-02700
Nut F2300-10000

213588

6-18
 CLUTCHES

3.6.2 Inspection and Repair

(1) Pressure plate

(a)Check the friction surface of the pressure plate
for burns and groove marks.
(b)Check the friction surface of the pressure plate
for distortion. Grind the surface if necessary.
(c)After grinding the friction surface of the pres-
sure plate, measure its thickness. Replace the
pressure plate if its thickness has been
reduced to the service limit.
213575
A: Standard value B: Repair or service limit
Item Dry-type Wet-type
A 22.8 mm 22.8 mm
Pressure plate thickness
B 21.0 mm 21.0 mm

(2) Pressure spring Replace if this

Check the pressure springs for deformation, dam- clearance exceeds
age and permanent set in fatigue. Replace if nec- 3 mm
essary.

213589

A: Standard value
Item Dry-type Wet-type
S4Q2 S4S S4S, S4Q2
Engine mounted
K21 K25 K25, K21
Free length of pressure spring mm A 93.2 106.4 78.8
Installed load/installed length N/mm A 257 ± 5% / 45.2 319 ± 5% / 45.2 643 ± 5% / 48.2

(3) Clutch cover

Check the clutch cover for distortion, cracks,
deformation and wear.

213590

(4) Release levers

Check each release lever for wear or damage on
the contact and sliding surfaces.

6-19
CLUTCHES

3.6.3 Reassembly
To reassemble, follow the disassembly sequence in
reverse. Also follow the instructions given below.
(1) Tightening bolts
(a)Tighten the bolts with strap fixing washers 3 to
the torque specified below.

A: Standard value
Item Dry-type Wet-type
Tightening torque A 39 to 59 N·m

(b)Tighten the bolts that hold locking plates 1 to

the torque specified below.

A: Standard value
Item Dry-type Wet-type
Tightening torque A 5.8 to 7.8 N·m

(2) Applying grease

Apply molybdenum disulfide grease (Never Seez
or equivalent) to the pressure plate of the dry-type
clutch at the following places.
(a)Contact surfaces of release lever and
pressure plate
(b)Contact surfaces of release lever and
lever support. Also apply anti-seize & lubricat-
ing compound (Never Seez grease) to the fol-
lowing parts.
(c)Threaded part of support nut
(d)Spherical part of support nut
(3) Installing pressure plate assembly
40
(a)Identifying by identification mark (Gasoline
M10×1.5
engine, dry-type clutch)

5
Item Dry-type Wet-type 10
Unit:mm
S4Q2 S4S S4S S4Q2
Engine mounted
K21 K25 K25 K21
Identification mark Yellow Blue Brown Pink
12 12 12 10
Pressure Spring pieces pieces pieces pieces
213588
(b)Using bolts as special tools (for removal and
installation of pressure plate), compress the
pressure springs and install the pressure plate
assembly into place in the clutch housing.

Special tool needed

Bolt 91268-01900
Washer 92301-02700
Nut F2300-10000

6-20
 CLUTCHES

3.7 Clutch Master Cylinder (Dry-Type Clutch)

3.7.1 Disassembly

7
3

2
1

5 8

213591
Disassembly sequence
1 Clevis 5 Snap ring
2 Lock nut 6 Piston assembly
3 Push rod 7 Filler union
4 Boot 8 Cylinder body

Suggestions for Disassembly

Note:(a)Use the repair kit for scheduled replacement
of parts 4 through 6.
(b) Replace the lock nut 2 and push rod 3 as a
set.

CAUTION
(1) Use care not to damage the cylinder, piston,
cups, etc.
(2) Do not take apart the piston assembly.
(3) Do not press the outer wall of the cylinder body
with a vice or the like.

6-21
CLUTCHES

3.7.2 Inspection and Repair (4) Push rod

(1) Cylinder body (a)Check the push rod for bending and deforma-
tion. Replace if defective.
(a)Check the inside surfaces for scratches,
uneven wear and corrosion.
(5) Boot
(b)Check the inlet and relief ports for condition.
Also check the joint for damaged threads. (a)Check the boot for cracks, damage and tear.
Replace if defective.
(2) Piston assembly (b)Check the boot for interference with the cylinder
Note:The piston assembly must be replaced periodi- and push rod. Replace the boot if it has no or
little interference.
cally. It is a safe and good practice to replace it
whenever the piston assembly is disassembled. (6) Filler union
(a)Check the sliding surfaces for scratches, (a)Check the filler union for cracks and scars.
uneven wear and damage. Repair the piston if Replace if any size of crack or scar is found.
defect is minor or replace if damaged. (b)Check the filler union for deformation. Replace
(b)Check the piston cups for damaged lip, chafed if excessively deformed.
base, wear and swelling. Replace if defective
using the repair kit. 3.7.3 Reassembly
(c)Measure the clearance between the piston and
To reassemble, follow the disassembly sequence in
cylinder body. Replace the piston assembly
reverse. Also follow the instructions given below.
together with the cylinder body if the measure-
ment exceeds the service limit. (1) Wash all metal parts with volatile cleaning solvent,
and completely dry them with compressed air.
A: Standard value B: Repair or service limit (2) Apply a thin coat of rubber grease (METAL RUB-
Clearance between piston A 0.016 to 0.086 mm BER #20) or brake fluid to the inside surface of
and cylinder body B 0.15 mm cylinder body, the peripheral surface of piston
cups and the cylinder body end surface. When
(d)Check the piston cup for interference. Replace applying grease, be careful, as piston seal if
the piston cup using the repair kit if the interfer- exposed to mineral oil will swell up.
ence is less than the service limit. (3) Be careful not to damage the lips of piston cups.

A: Standard value B: Repair or service limit

A Approx. 1.0 mm
Primary cup
Piston cup B 0.4 mm
interference A Approx. 1.1 mm
Secondary cup
B 0.4 mm

(3) Return spring

(a)Check the return spring for scars, wear and per-
pendicularity. Replace if defective.
(b)Measure the free length of the return spring.
Replace if the measurement exceeds the ser-
vice limit.

A: Standard value B: Repair or service limit

A 81 mm
Free length of return spring
B 74.2 mm

6-22
 CLUTCHES

3.8 Clutch Release Cylinder

3.8.1 Disassembly

4
3 8

213592
Disassembly sequence
1 Air bleeder valve 5 Boot
2 Clevis 6 Piston assembly
3 Lock nut 7 Spring
4 Release rod 8 Cylinder body

Suggestions for Disassembly

Note:(a)If the piston assembly is hard to remove, sup-
port the end face of the cylinder body and
gradually introduce low-pressure air from the
port. This should enable the piston assembly
to be easily removed.
(b) When replacing periodic replacement parts, 5,
6 and 7, use the repair kit, and apply grease to
the sliding surfaces and outer areas. When re-
placing these parts with ones in repair kit, ap-
ply grease to them.
(c) Replace the clevis 2, lock nut 3 and release
rod 4 as a set.

CAUTION
(1) Use care not to damage the cylinder, piston,
cups, etc.
(2) Do not take apart the piston assembly.
(3) Do not press the outer wall of the cylinder body
with a vice or the like.

6-23
CLUTCHES

3.8.2 Inspection and Repair (5) Push rod

(1) Cylinder body (a)Check the push rod for bending and deforma-
tion. Replace if defective.
(a)Check the inside surfaces for scratches,
uneven wear and corrosion.
(6) Boot
(b)Check the port for condition and damaged
threads. (a)Check the boot for cracks, damage and tear.
Replace if defective.
(2) Piston assembly (b)Check the boot for interference with the cylinder
Note:The piston assembly must be replaced periodi- and push rod. Replace the boot if it has no or
little interference.
cally. It is a safe and good practice to replace it
whenever the piston assembly is disassembled.
3.8.3 Reassembly
(a)Check the sliding surfaces for scratches, To reassemble, follow the disassembly sequence in
uneven wear and damage. Repair the piston if reverse. Also follow the instructions given below.
defect is minor or replace if damaged.
(1) Wash all metal parts with volatile cleaning solvent,
(b)Check the piston cups for damaged lip, chafed
and completely dry them with compressed air.
base, wear and swelling. Replace if defective
(2) Apply a thin coat of rubber grease (METAL RUB-
using the repair kit.
BER #20) or brake fluid to the inside surface of
(c)Measure the clearance between the piston and
cylinder body and the peripheral surface of piston
cylinder body. Replace the piston assembly
cups. When applying grease, be careful, as piston
together with the cylinder body if the measure-
seal if exposed to mineral oil will swell up.
ment exceeds the service limit.
(3) Use care not to let foreign matters enter the cylin-
A: Standard value B: Repair or service limit der body. Also be careful not to damage the cylin-
der body and the lip of piston cup.
Clearance between piston A 0.020 to 0.105 mm
(4) Tighten the following parts to the specified
and cylinder body B 0.15 mm
torques.

Air bleeder valve

(d)Check the piston cup for interference. Replace
the piston cup using the repair kit if the interfer- 7 to 9 N·m
Tightening torque
(0.7to 0.9 kgf·m)
ence is less than the service limit.

A: Standard value B: Repair or service limit Lock nut

A Approx. 1.8 mm 15 to 17 N·m
Piston cup interference Tightening torque
B 0.4 mm (1.5 to 1.7 kgf·m)

(3) Spring
(a)Check the return spring for scars, wear and per-
pendicularity. Replace if defective.
(b)Measure the free length of the spring. Replace
if the measurement exceeds the service limit.

A: Standard value B: Repair or service limit

A 43 mm
Free length of spring
B 39.4 mm

(4) Air bleeder valve

(a)Check the air bleeder valve for damaged or
deformed seat. Replace if defective.
(b)Check the air bleeder valve for cracked or dete-
riorated cap. Replace if defective.

6-24
 CLUTCHES

4. Adjustment
4.1 Bleeding Clutch Hydraulic System
Bleeding the hydraulic system of the clutch is a two-
man operation. Start the engine, then proceed to bleed
the system with the engine idling.

Vinyl tube
Brake fluid

Jar

213593

(1) Fill the reservoir with brake fluid. Keep the reser- Precautions
voir more than half full of fluid during bleeding (1) Maintain the proper fluid level in the reservoir dur-
operation. ing bleeding operation.
(2) Remove the bleeder cap. Connect one end of a (2) Use care not to spill brake fluid on painted sur-
transparent vinyl tube (6mm in inside diameter) to faces.
the bleeder valve. Place the other end of the tube (3) When refilling the reservoir, do not mix different
into a transparent jar filled with brake fluid. (Be types of brake fluid.
sure that the tube is in the fluid.) (4) Connect the vinyl tube liquid-tight.
(3) One person slowly pumps the clutch pedal full (5) After bleeding, refill the reservoir slowly up to the
stroke several times. Hold the clutch pedal down specified liquid level.
after depressing for the last time. (6) Release the clutch pedal slowly. If not, air could
(4) The other person loosens the bleeder valve with a be drawn back into the system.
wrench (10mm). This causes the brake fluid in the (7) Do not remove foot pressure from the clutch pedal
system to flow out with trapped air into the jar. before tightening the bleeder valve.
(5) Tighten the bleeder valve and slowly remove foot (8) Do not reuse the brake fluid in the jar. It may con-
pressure from the clutch pedal. tain foreign substances like dirt.
(6) Repeat the steps (3), (4) and (5) until no more air
bubbles are seen in the jar.
(7) Reinstall the bleeder cap and refill the reservoir
with the brake fluid up to the specified level.

6-25
CLUTCHES

4.2 Clutch Pedal Adjustment (Dry-Type)

Lock nut

Reservoir Stopper
bolt

Clutch pedal height

Frame top

Clutch master cylinder

0 to 1mm

Clevis Clutch release

cylinder
Lock nut
Push rod

213594

(1) Bleed the clutch release cylinder of trapped brake (4) Adjust the length of the push rod for a clearance
fluid and air through the bleeder valve (between of 0 to 1mm between its rear end and the push
reservoir and clutch master cylinder and release rod contact face of the piston in the clutch master
cylinder). cylinder. Secure the push rod in that position with
(2) Using the stopper bolt, adjust the height from the the lock nut.
top surface of the floor plate to the top of the (5) Apply finger pressure to the clutch pedal and if it
clutch pedal to the standard value specified travels to a point where it feels heavy (play) it is
below. Hold the clutch pedal at that height. within specified standard limits.

A: Standard Value A: Standard Value

Height of clutch pedal A 191.6 mm Clutch pedal free play A 0 to 6 mm

(3) Loosen the lock nut holding the clevis on the front
end of the push rod.

6-26
 CLUTCHES

4.3 Clutch Pedal Adjustment (Wet-Type)

Lock nut
Reservoir
Stopper
bolt

Clutch pedal height

Frame top

Hydraulic booster

0 to 1mm

Clevis Clutch release

cylinder
Lock nut

Push rod

213595

(1) Bleed the clutch release cylinder of trapped brake (4) With the engine stopped, pump the clutch pedal a
fluid and air through the bleeder valve (between few times to release pressure from the booster.
reservoir and clutch master cylinder and release Then, apply finger pressure to the clutch pedal to
cylinder). see if it travels to a point where it feels heavy
(2) Using the stopper bolt, adjust the height from the (play) it is within the specified standard limits.
top surface of the floor plate to the top of the
clutch pedal to the standard value specified A: Standard Value
below. Hold the clutch pedal at that height. Clutch pedal free play A 0 to 6 mm

A: Standard Value Note:If the free play is less than the specified limit, the
Height of clutch pedal A 191.6 mm push rod thrusting at the piston of the clutch mas-
ter cylinder blocks the return port to cause half
(3) Loosen the lock nut of the operating rod. Adjust
clutching, resulting in premature wear of the
the length of the operating rod for a clearance of 0
to 1mm between its rear end and the rod contact clutch facings. If the free play is more than the
surface of the booster valve plunger. Secure the specified limit, the operating rod needs a longer
operating rod in that position with the lock nut. length of engagement with the clevis.

6-27
CLUTCHES

4.4 Checking Clutch Disc for Wear

The clutch release cylinder automatically compen-
sates for changes in the position of the release levers
of the pressure plate due to wear of the clutch disc.
While there is no need for further pedal adjustment
once the pedal is adjusted at the time of assembly, it is
recommended that wear loss be periodically mea-
sured to determine the time to replace the clutch disc.

Piston

Push rod complete Boot Cylinder body

L2 L1

213596
1 liter: Length when release cylinder is assembled (mm)
L1: Length when release cylinder is installed to clutch shifter shaft (when clutch disc is new)
L2: Distance between centers of cylinder body mounting bolt hole and mounting pin hole

(1) After the clutch release cylinder is installed with Dimension L1 (reference) A: Standard value
the clutch pedal adjustment procedure described
Dry-type clutch A 22 mm
above, measure L2 and record the measurement.
Wet-type clutch A 17 mm
Note:L2 can deviate from the specified standard limits
due to error in the installed dimensions of parts, Dimension L2 A: Standard value
their free play, etc. Dry-type clutch A 105.9±0.5 mm
(2) As the clutch disc wears, the piston is pushed in Wet-type clutch A 100.9.±0.5 mm
further little by little with a gradual decrement of
L2. At every monthly check, measure L2 and if the
measurement exceeds the specified service limit,
replace the clutch disc.

6-28
 CLUTCHES

5. Troubleshooting

Clutch facings worn Replace the clutch disc.

Wipe with cloth soaked with suitable clean-
Greasy deposits on clutch facing (dry-type clutch only) ing solvent or alcohol, or replace the clutch
disc.

Clutch slips Burnt, grooved, warped or unevenly worn of pressure plate, fly- Disassemble and repair, or replace if neces-
wheel, clutch discs sary.
Broken or fatigued pressure springs Replace the spring.
Failure of clutch pedal to return Disassemble and repair.
Improper clutch pedal linkage system adjustment Readjust.

Slip test (manual transmission models)

Apply parking brake to hold truck locked still; disengage clutch; shift transmission into forward second; and pick up
engine speed while slowly releasing clutch pedal to see if engine stalls. If engine stalls, clutch is not slipping. A slip-
ping clutch is indicated by engine not stalling (with truck held standstill).

Release lever unequal height Adjust the height of lever.

Clutch disc not sliding smoothly on clutch shaft due to seizure or
Repair or replace if excessively worn.
local wear of sliding surfaces of splines.
Scuffing movement of clutch shifter on clutch shaft (dry-type
Apply grease to sliding faces.
clutch).
Clutch drags
Release bearing seized stiff and not rotating. Replace the bearing.
Wobbly or broken clutch disc. Replace the clutch disc.
Badly worn or damaged pilot bearing. Replace the bearing.
Clutch shifter seized on input shaft
Repair or replace if necessary.
(Wet-type clutch only)

Drag test (manual transmission models)

Disengage clutch; shift transmission into forward first; shift back to neutral; depress accelerator pedal to pick up
engine speed; and shift transmission again into forward first (while keeping clutch pedal depressed). If gear grating
occurs with the last shifting, clutch has a dragging tendency or is dragging.

Release lever unequal height Adjust the height of lever.

Clutch makes abnor-
mal noise when disen- Release levers worn or seized. Replace the release lever.
gaged
Pilot bearing worn. Replace the bearing.
Thrust plate of pressure plate broken, or strap rivets or bolts
Replace straps and bolts.
loose.
Clutch makes abnor-
mal noise when Clutch disc torsion springs weak or damaged. Replace the clutch disc.
engaged.
Retighten, or replace if cushion rubber is
Engine mounting loose or cushion rubber damaged.
remarkably deteriorated.

6-29
CLUTCHES

Clutch facing glazed or hardened. Replace the clutch disc.

Wipe with cloth soaked with suitable clean-
Greasy deposits on clutch facing (dry-type clutch only) ing solvent or alcohol, or replace the clutch
disc.
Clutch chatters Clutch disc torsion springs damaged. Replace the clutch disc.
Clutch facings not contacting uniformly or disc wobbles. Replace the clutch disc.
Disc rivets loose. Retighten.
Pressure plate flywheel distortion Repair or replace.
Wipe with cloth soaked with suitable clean-
Greasy deposits on clutch facing (dry-type clutch only) ing solvent or alcohol, or replace the clutch
disc.
Clutch facings worn or rivets loose Replace the clutch disc.
Clutch shudders
Clutch facing rivets exposed Replace the clutch disc.
Torsion springs damaged Replace the clutch disc.
Release levers worn unevenly. Replace the release lever.
Engine oil leaking into clutch housing (dry-type clutch), or
hydraulic oil and engine oil mixed (wet-type clutch).
(1) Engine rear seal damaged. Replace the rear seal.
Oil leakage
(2) Seal case gasket damaged. Replace gasket.
Oil leaking at the joint between engine cylinder block and rear
Replace gasket.
plate.
Vacuum hose joint loose. Retighten.
Vacuum hose flat or ruptured. Replace the hose.
Inclusion of foreign matter of valve damage in the vacuum valve
Clutch pedal hard to Repair or replace.
and atmospheric pressure valve of clutch booster.
push down
Clutch booster element clogged. Clean or replace.
Clutch booster diaphragm defective Replace.
Entry of foreign matter inside clutch cylinder. Clean and refill the cylinder.
Lack of clutch cylinder fluid. Refill.
Pedal feels spongy Clutch cylinder fluid leaks Repair or replace.
Air trapped in system Bleed the air.

6-30
 CLUTCHES

6. Service Data
6.1 Dry-Type Clutch
A: Standard value B: Repair or service limit
Unit: mm
Truck type
Item
1 ton class 2 ton class 3 ton class
Clutch pedal Pedal height from floor panel 1
A 191.6
(from the top of pedal pad to the frame top)
Clutch pedal free play 2 A 0 to 6

Frame top

0 to 1 mm

213597

Input shaft Spline diameter 1 A 0

27.25 -0.2
Free movement of clutch disc (looseness of mating
splines) at rim of disc. B 6

213598

Clutch disc A 9.2±0.3

Facing thickness 1 Each side: 2.3
B
Both sides: 7.1
Disc runout (at rim) A 1.0 or less

Both
Each

213599

6-31
CLUTCHES

A: Standard value B: Repair or service limit

Unit: mm
Truck type
Item
1 ton class 2 ton class 3 ton class
Clutch Inside diameter of cylinder body 1 A 15.87
master
A 0.016 to 0.086
Cylinder Clearance between piston and cylinder 2
(dry-type) B 0.15
Secondary cup outside diameter 3 A 17.0±0.2
Free length of return spring 4 A 81

2 3

1 4
213600

Clutch Inside diameter of cylinder body 1 A 19.05

master
A 0.020 to 0.105
Cylinder Clearance between piston and cylinder 2
(wet-type) B 0.15
Secondary cup outside diameter 3 A 20.2±0.2
Free length of return spring 4 A 81.3

4 1

3
215200

6-32
 CLUTCHES

A: Standard value B: Repair or service limit

Unit: mm
Truck type
Item
1 ton class 2 ton class 3 ton class
Clutch Inside diameter of cylinder body 1 A 22.22
release
A 0.020 to 0.105
Cylinder Clearance between piston and cylinder 2
(for both wet & B 0.15
dry-types) Diameter of piston cup A 24±0.2
Free length of return spring A 43

213601

6-33
CLUTCHES

A: Standard value B: Repair or service limit

Unit: mm
Truck type
Item
1 ton class 2 ton class 3 ton class
Pressure A 0.05 or less
Plate Flatness of plate
B 0.2

Thickness of plate 1 A 22.8

(from spring seat to friction surface) B 21

Height of release lever 2 A 26.5

(with 2.1mm of the disc wear amount) B 16.5
Maximum permissible difference between heights of
A 0.7
all release levers 3
Quantity per clutch A 12
S4Q2, K21engine mounted: 93.2
Pressure Free length A
S4S, K25 engine mounted: 106.4
spring 4
Installed load/ S4Q2, K21engine mounted: 257± 5%/45.2
N/mm A
installed length S4S, K25 engine mounted: 319 ± 5%/45.2
Washer mounting bolt
N•m A 39 to 59
tightening torque 5
Lock plate mounting bolts
N•m A 5.8 to 7.8
tightening torque 6
Pressure plate
N•m A 17
tightening torque 7

1
4

6 2

7
213602

6-34
 CLUTCHES

6.2 Wet-Type Clutch

A: Standard value B: Repair or service limit
Unit: mm
Truck type
Item
1 ton class 2 ton class 3 ton class
Clutch pedal Pedal height (from frame to the top of pedal pad)1 A 191.6
Free play 2 A 0 to 6

214080

Input shaft Spline diameter 1 A 0

27.25 -0.2
Free movement of clutch disc (looseness of mating
B 1
splines) at rim of disc

213598

Clutch disc A 6.0±0.3

Facing thickness (total) 1 Each side: 1.6
B
Both sides: 5.2
Disc runout (at rim) A 0.7 to 1.1

1
Both
Each

213604

6-35
CLUTCHES

A: Standard value B: Repair or service limit

Unit: mm
Truck type
Item
1 ton class 2 ton class 3 ton class
Pressure A 0.05 or less
Plate Flatness of plate
B 0.2

Thickness of plate 1 A 22.8

(from spring seat to friction surface) B 21.0
Height of release lever 2 A 26.5
Maximum permissible difference between heights of
A 0.7
all release levers 3
S4S, K25 engine mounted: 12
Quantity per clutch A
Other models: 10
Pressure
Free length A 78.8
spring 4
Installed load/
N/mm A 643 ± 5%/48.2
installed length
Strap bolt tightening torque 5 N·m A 39 to 59
Lock plate mounting bolts
N·m A 5.8 to 7.8
tightening torque 6
Pressure plate
N·m A 17
tightening torque 7

1
4 7

213605

6-36