Failure Diagnosis

The LuK guide to troubleshooting

clutch system failures and
malfunctions on agricultural vehicles
The content of this brochure shall not be legally binding Copyright ©
and is for information purposes only. To the extent legally Schaeffler Automotive Aftermarket GmbH & Co. KG
permissible, Schaeffler Automotive Aftermarket GmbH March 2016
& Co. KG assumes no liability out of or in connection with
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All rights reserved. Any copying, distribution, reproduc-

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Contents

Page

1 The LuK guide to troubleshooting tractor clutch failures 6

2 What is clutch drag? 7

3 What is clutch slip? 8

4 What is clutch judder? 9

5 What is clutch noise? 10

6 Single clutch with independent drive for P.T.O. (split torque) 11

7 Combined clutch for tractors (special design) 12

8 Double clutch with independent P.T.O. 13

9 Twin plate clutch for transmission drive 14

10 Single safety P.T.O. clutch with fixed transmission damper 15

11 Double clutch with safety P.T.O. 16

12 Front P.T.O. clutch 17

13 Long travel torsion damper 18

14 Axial spring torsion damper 19

15 Drive disc (with sintered or organic friction) 20

16 Concentric Slave Cylinder (CSC) 21

3
 24/7
LuK Tractor Clutches:
No. 1 in the field at all times !
The genuine LuK portfolio has the right parts for every possible use
– OE quality and operational comfort included. LuK is the leading
manufacturer of clutch technology, supplying all major tractor
­manufacturers worldwide. LuK damping systems provide a highly
effective system to dampen vibrations. Rely on our cost effective
products with prolonged operating life. Have the freedom to work
your field 24/7.

4
We move the world – with quality.
Schaeffler Automotive Aftermarket is a specialist in components and
services involving the complete drivetrain in passenger cars and
commercial vehicles – from engines, to transmissions, to chassis. As a
globally active company we move millions of people every day in cars,
trucks, buses, and tractors. Our products are used in almost every new
vehicle throughout the world – and for good reason: Schaeffler is the
innovation-leader in original equipment manufacturing and aftermarket
sales – and is a guarantee of the very highest quality.

5
1 The LuK guide to troubleshooting tractor clutch failures

This guide is for the use of anyone who sells, installs or reports on LuK agricultural clutches. It is intended to be a
source of information that can help simplify the diagnosis of clutch failures and malfunctions. The content is confined
to the most common cause of tractor clutch defects and is not designed to be a comprehensive list. Technical
diagrams are generic examples of the type of product and for guidance only.

Major causes of problems

Clutch cable
Flywheel • It is advisable to replace cables whenever clutches are
• The surface face of the flywheel may show signs of replaced.
scoring, glazing, and/or gouges. • Make certain that clutch cables are correctly routed
• This must be refaced to the tolerances laid down by the when installing them.
manufacturer.
• It is important that the same amount is refaced from Concentric Slave Cylinder (CSC)
the clutch mounting surface. • Always use the vehicle manufacturer’s specification
• Also take this opportunity to check the starter ring gear. and recommendation of clutch fluid.

Spigot (pilot) bearing Alignment

• Binding or seized bearings will cause the clutch to not • Always use the correct aligning tools when installing
disengage. the clutch and disc to avoid spline or disc damage.
• Collapsed bearings will cause noise and angular
misalignment of the input shaft, and thus cause Lubricants
damage to the driven disc. • Grease that contains no suspended metallic
particulates should be used for lubricating splines and
Oil seals release bearings/guide tubes.
• Leaking oil seals are a major cause of clutch failure. • LuK can supply the correct high-melting-point grease
for clutch replacements.
Clutch disc Please order LuK Part No. 414 0014 10.
• Before installation, each disc should be checked for • Once grease has been applied to the splines on the
lateral runout (max. permissible 0.5 mm). gearbox input shaft, slide the driven disc hub onto the
shaft and remove any excess grease.
Release mechanism
• Release bearings should always be renewed whenever
the clutch is replaced.
• The bearings should slide freely on their guide tube
without tilting.
• Check the guide tube, for correct fitment. Guide tubes
should be concentric to the transmission input shafts.
• All bearing carriers and release forks must be free of
wear to their pivots.
• Excessive play in release shaft bushes reduces release
bearing travel.
• Worn, bent, or broken release forks may prevent the
clutch from disengaging.
• Lubricate all moving parts.

6
2 What is clutch drag?

One function of the clutch is to interrupt the drive from the engine to the transmission, which allows
the operator to select and engage each gear smoothly. If clutch drag occurs the operator will
experience difficulty in selecting or changing gear without grating.

Possible causes Remedy

Excessive clutch pedal or hand clutch lever
Refer to operator’s manual for correct settings
free play
Air in the system will reduce the thrust bearings release travel –
Air in hydraulic release system
Bleed air from the system and ensure that the correct fluid is used

Master & slave cylinder adjustment / fault Check for external leaks, push rod adjustment and binding linkage

Check for external leaks, bleed air from the system and ensure that the correct fluid
Concentric Slave Cylinder (CSC) fault
is used
Insufficient clutch pedal or hand lever
Check the pedal and lever stop settings and for linkage fouling
release travel
Bolts are factory set and depending on flywheel and disc condition they may require
PTO second stage setting bolts
additional adjustment during fitment to the tractor

Clutch cable stretched / collapsed A faulty cable will reduce the movement of the release bearing – Replace the cable

Flywheel bearing seized / tight Always replace the bearing

Clutch housing centre bearing seized / tight Always replace the bearing

Incorrect disc centering on assembly Use correct alignment tool when installing the clutch and disc to flywheel

Clutch release cross shaft and bushes worn Excessive wear will not allow even or full clutch release travel – Replace worn parts

Clutch release fork worn or loose Check release fork pivots for excessive or uneven wear

Clutch disc friction loose or damaged Check that the friction riveting is secure and friction face is flat and even

Clutch disc friction contaminated Contaminated discs must be replaced

Disc may be distorted during transport, during installation or by exposure to severe

Clutch disc distorted
heat input in service – Replace the disc
Straps must not be kinked or show gaps between the leaves –
Pressure plate tangential straps damaged
Any deformity will result in the pressure plate not lifting sufficient or evenly

Uneven clutch pressure plate lift Caused by damaged tangential pressure drive straps or incorrectly set clutch levers

Fault within transmission Worn or broken synchro rings – Lubrication level too low

Ensure splines are free of all burrs, damage and rust – Lightly lubricate splines –
Transmission input shaft splines
use LuK spline grease ref. 414 0014 10

Disc splined hub damaged / tight

Splines damaged during assembly
or by gearbox misalignment.

7
3 What is clutch slip?

Another function of the clutch is to transmit the drive from the engine through the clutch into the transmission
without any loss of power. Clutch slip occurs when the speed of the engine differs to that going into the t­ rans-
mission. This is evident by the engine revs increasing but the wheel or PTO speed failing to increase accordingly.

Possible causes Remedy

The clutch disc friction has worn below its limits and the rivets have contacted
Clutch disc friction worn out the pressure plate face. The clutch disc has achieved a full service life –
Replace clutch disc

The clutch disc friction has been damaged or destroyed through excessive
Clutch disc friction damaged
heat input from slip or contamination – Replace clutch disc

The friction material is contaminated with oil or grease – Excessive spline lubrication
Clutch disc friction contaminated applied during tractor assembly or the engine crankshaft / gearbox oil seal is leaking
– Replace the clutch disc

The clutch assembly diaphragm spring provides the clamping force for the clutch –
Clutch clamp load reduced Excessive heat input into the clutch will destroy the diaphragm spring –
Replace the clutch

Binding within the clutch Pressure plate lugs binding in the clutch housing

Release system has no free play causing the clutch to run partially disengaged,
Incorrect release system adjustment resulting in increased heat input to the friction disc due to clutch slip –
Check the free-play adjustments

Incorrect adjustment can result in excessive release bearing pre-load resulting in

Hydraulic release systems
clutch slip – Check that the master and slave cylinder adjustments are correct

Check that the release system has sufficient movement and that there is no fouling –
Release system binding or fouling
Lubricate all pivots and bushes – Check the cables for binding

The Tractor is being used for operations beyond its design capabilities –
Tractor being used for incorrect work load Including: Towing too heavy a load – Operating external machinery that requires
a greater HP (Kw) rating – Excessive front end loader work

The operator can be responsible for inducing clutch slip via a poor driving style –
Operator driving error
Do not rest anything on the clutch pedal!

Check for any obstructions that may prevent a full pedal stroke
Restricted pedal travel
Check the pedal stop adjustment

Condition of the flywheel wear face

It is recommended that all flywheel wear
faces must be refaced and any location
step or pot depth must be re-established
when the clutch is replaced – However,
worn, uneven, grooved or highly polished
wear surfaces must always be refaced.

8
4 What is clutch judder?

Clutch vibration (or clutch judder) is experienced by the operator during the engagement of the clutch. When
this occurs it will be difficult for the operator to achieve a smooth take-up of drive and deliver precise tractor
movements.

Possible causes Remedy

Friction material retaining rivets are loose due to aggressive clutch engagement –
Clutch disc has loose friction
Replace the clutch disc

Some clutch discs use cushioning segments between the riveted friction
Clutch disc cushioning damaged (to assist a smooth engagement of drive) which can be destroyed by high heat input
– Replace the clutch disc

Check that the disc is flat and has no sign of distortion – Damage can occur during
Clutch disc bent or distorted
transit or as a result of sub-standard installation

Caused by incorrectly set clutch levers or by an uneven flywheel wear face or clutch
Clutch lever heights not even
mounting face – Ensure uneven or highly polished wear surfaces are refaced

Caused by an uneven flywheel wear face, the clutch mounting face is not flat or the
Diaphragm spring fingers uneven
fulcrum ring has dislodged

The build-up of dust can cause excessive friction in the moving parts of the clutch –
Clutch pivots binding Additionally, the levers, pivots or diaphragm fulcrum points can also be affected
by rust, causing heavy clutch operation

Reface the flywheel wear face to within 0.1mm and re-establish any pot or
Flywheel wear face uneven
location step

Release system linkage / cable binding Check all linkages are free and lubricated – Replace the cables

Care must be taken during clutch installation to ensure that the cover and discs
Damaged hub splines
are correctly aligned using special tools – Discs must be free moving on the splines

Wear to release bearing, carrier and A loose or worn release bearing and carrier can vibrate during operation and may
support snout make contact with the fork or support snout

External influence – Cab mounts Loose / worn cab mountings or wear in the tractor driveline

The friction material is either contaminated with oil or grease caused by excessive
Clutch disc friction is contaminated spline lubrication applied during tractor assembly or the engine crankshaft / gearbox
oil seal is leaking – Replace clutch disc

Clutch disc torsion damper faulty

Damper springs can be damaged
during installation due to poor gearbox
alignment or coil spring breakage from
excessive torque loadings – Replace
the clutch disc.

9
5 What is clutch noise?

Clutch noise may be as a result of parts failure or system wear. Noise during clutch disengagement is normally
related to the release system. However, noise during engagement and drive is usually related to disc cushioning
or damping.

Possible causes Remedy

Faulty release bearing Replace the release bearing

Release bearing retainer clip or spring

Replace the damaged components
damaged

The first stage damper which controls engine idle damping may have loose or broken
Clutch disc idle torsion damper defective
coil springs as the result of an aggressive driving style or poorly tuned engine

The second stage damper controls and absorbs the vibration generated by the engine
Clutch disc secondary main torsion and prevents it from entering the transmission drivetrain – Failure can also be caused
damper defective by the disc reaching the end of its service life, an aggressive driving style, excessive
torque loadings or material failure

Badly worn splines Excessive spline wear can cause the disc to ‘chatter’ or vibrate

Cushioning between the clutch disc friction has collapsed due to high heat input,
Clutch disc cushioning defective
resulting in a high pitched engagement ‘squawk’

Wear or damage within the tractor drive line or transmission causing noise and
External influence
vibrations, or loose cab mountings causing the cab to foul against the chassis

Flywheel / centre bearing collapsed or

Replace the affected bearings
seized

Ensure the clutch disc is fitted the correct way round in accordance with the
Clutch disc incorrectly fitted
product markings

Incorrectly installed release bearing

Release bearing fouled due to incorrect
installation – Ensure the bearing is
aligned correctly and fitted the right way
round.

10
6 Single clutch with independent drive for P.T.O. (split torque)

1 1 Cover housing
2 Pressure plate
7 3 Diaphragm spring
(with reinforced fingers)
8 4 Fixed P.T.O. hub
5 Rivet
6 6 Fulcrum ring
7 Tangential strap
5 8 Headed rivet

11
7 Combined clutch for tractors (special design)

10

2 15

7 10

6 17

3 14

13

4 12

16

11 9

1 1 Cover housing
2 P.T.O. pressure plate
8 15 3 Flywheel plate
4 Pressure plate (transmission)
3 8 5 Diaphragm spring
6 Coil spring
14 7 P.T.O. disc (with organic friction)
8 Pivot pin
13 9 Fixing hole
10 Shipping bolt
17 11 P.T.O. adjusting screw
12 Link
13 Clutch lever
14 Anti-rattle spring
15 15 Lever adjustment screw
16 Balance hole
17 Rivet

6 5

11 2

12
8 Double clutch with independent P.T.O.

8 14

13

2 1

13

15 9

3 14

1 8 1 Cover housing
2 Main drive
12 14 pressure plate
3 P.T.O. pressure plate
3 13 4 Diaphragm spring
5 Main drive clutch disc
2 7 (with sintered pads
and torsion damper)
5 6 Main drive lever
7 P.T.O. lever
4 8 P.T.O. lever eyebolt
9 Transmission lever
elbow
10 Adjusting screw
11 Lock nut
15 12 Adjusting nut
13 Anti-rattle spring
14 Pivot pin
6 15 Fulcrum ring
2
9
11
14
10
14

13
9 Twin plate clutch for transmission drive

2 1

5 13

18 7

15 16

4 7

15 8

6 14

17

14 13

8 1 1 Cover housing
2 Main drive pressure plate
12 14 (transmission side)
3 Main drive pressure plate
4 13 (flywheel side)
4 Diaphragm spring
3 7 5 Main drive clutch disc with
sintered pads and torsion
2 5 damper (transmission side)
6 Main drive clutch disc with
15 sintered pads and torsion
damper (flywheel side)
18 18 7 Main drive lever
8 Transmission lever eyebolt
4 9 Transmission lever elbow
10 Adjusting screw
6 3 11 Lock nut
12 Adjusting nut
3 7 13 Anti-rattle spring
14 Pivot pin
15 9 15 Fulcrum ring
16 Rivet
11 14 17 Balance hole
18 Disc spline
10 13

14
10 Single safety P.T.O. clutch with fixed transmission damper

2 1

10

12

3 11

3 1 1 Cover housing
2 P.T.O. pressure plate
9 11 3 P.T.O. coil spring
4 Fixed transmission damper
2 7 5 Friction device
6 P.T.O. lever
1 7 Pivot pin
8 Anti-rattle spring
5 6 9 Adjusting nut
10 Transmission damper spring
4 11 P.T.O. lever eyebolt
12 Rivet

12

5 10

15
11 Double clutch with safety P.T.O.

15

4 1

9 15

3 8

16 10

7 17

11

16 1 1 Cover housing
2 Main drive pressure plate
14 10 3 P.T.O. pressure plate
4 Diaphragm spring
2 6 5 Main drive disc
(with sintered pads and
8 torsion damper)
6 Pivot pin
15 7 Main drive lever
8 P.T.O. lever
5 9 Fulcrum ring
10 P.T.O. lever eyebolt
11 Transmission lever elbow
12 Adjusting screw
9 13 Lock nut
14 Adjusting nut
2 7 15 Anti-rattle spring
16 Coil spring
3 15 17 Balance hole

4 1

12 11

13 6

16
12 Front P.T.O. clutch

11 1

3 10

4 9

6 2

8 9

10

12 10 1 Housing cover plate

2 Diaphragm spring
3 1 3 Separator discs
4 Drive discs
5 (with sintered pads)
5 Lower pressure plate
8 6 Secondary drive hub
7 Support bearing
7 2 8 Primary drive hub
9 Rivet
9 10 Housing bolt
11 Fulcrum ring
6 11 12 Coil spring

7 10

10

4 11

17
13 Long travel torsion damper

3 8

5 6

1 1. Location plate (primary)

2. Damper housing
4 3. Drive shaft location flange
(secondary)
2 4. Arc spring
5. Friction device
5 6. Location holes
7. Rivet
8 3 8. Central carrier plate
(secondary)
7

4 2

18
14 Axial spring torsion damper

1 2

7 9

6 4

11 3

10

3 1. Location plate (primary)

2. Carrier plate
(secondary)
3. Sensor wings
9 4. Torsion springs (idle)
5. Torsion springs
(second stage)
6. Torsion springs
4 5 (third stage)
7. Friction device
9 6 8. Location hole
9. Rivet
10. Splined drive hub
11. Backplate
10

11 2

19
15 Drive disc (with sintered or organic friction)

1 1 Friction pad
2 Friction backplate
2 3 Torsion damper spring
4 Splined drive hub
6 5 Carrier plate
6 Cushioned friction carrier plate
7 Friction device
8 Rivet
9 Cushion rivet

20
16 Concentric Slave Cylinder (CSC)

3 3

2 7

3 1 Housing
2 Release bearing
1 3 Hydraulic port
4 Piston
7 5 Piston seal
6 Pre-load spring
6 7 Plastic dust shield

21
Notes

22
Notes

23
 9882004010/05.2015
© 2016 Schaeffler Automotive Aftermarket GmbH & Co. KG

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