Always replace the complete clutch i.e. Cover Assembly, Driven Plate & Release Bearing.

Ensure that the correct parts are obtained, check against the original units before fitting.

Place the driven plate inside the cover assembly pressure plate the correct way round to ensure that no fouling occurs between the two components.

Always use a clutch alignment tool.

Never allow the weight of the gearbox to hang on the clutch components.

1. Check the spigot bearing thoroughly for excessive wear and replace if necessary.
2. Examine all components for signs of oil contamination, check and replace if necessary engine and gearbox oil seals.
3. Examine the old clutch plate splines for signs of excessive wear or damage; this may indicate previous gearbox misalignment.
4. Check the flywheel for run-out, scoring or cracking and excessive wear, abnormal and excessive clutch plate wear will occur unless this corrected.  If machining of the flywheel is undertaken ensure that the same amount of material is removed from both friction and mounting surfaces.  Flywheels with excessive wear should always be replaced.
5. Ensure that the clutch release mechanism operates freely, examine all release bearing mounting components (clutch release arm, cross shaft, bushes bearings etc) for excessive wear or damage.  Replace all substandard parts.
6. Ensure all contact surfaces are in good condition, and that oil or grease is not allowed to contaminate the contact surfaces.  Always remove any protective coating that may be applied to the clutch cover pressure plate.
7. Ensure that the driven plate is not damaged prior to fitting, lightly grease the spline and ensure that the driven plate slides freely on the gearbox spline.  Take care not to damage the spline on fitting.
8. Ensure that the driven plate is fitted the correct way round.
9. Use an alignment tool to position the driven plate centrally during fitment, do not remove the tool until all the cover assembly bolts have been tightened.
10. When re-fitting the cover assembly to the flywheel the mounting bolts must be tightened diagonally and not in rotation, ensure that the cover is located correctly onto the dowels and that any alignment marks or slots are matched correctly.
11. Before re-fitting the gearbox ensure that all gearbox dowels are in place and that they are not excessively worn.  Ensure that any dowel bolts are replaced in the correct location.
12. When offering the gearbox up to the engine take care not to damage the diaphragm fingers, release levers or release plate with the gear ox input shaft.
13. Ensure correct release bearing/clutch pedal adjustment, ensure correct pre-load with constant running types.  Always re-set any self adjusting mechanisms that may be fitted.
14. Check the condition of engine and gearbox mountings, replace if necessary.   Ensure there is no excessive backlash in the universal joints or the rear axle.
15. Check the condition of hydraulic systems and replace substandard parts.
16. Check the condition of the clutch cable and ensure that is has not stretched or frayed at any point, replace any substandard parts.

The Clutch System Components and Common causes of Failure.

Cover Assembly.

Damage of the diaphragm fingers by the gearbox input shaft during installation and over stroked diaphragms are common causes of cover assembly malfunctions.  Ensure when re-fitting the gearbox that this is carried out without damaging any of the clutch components.   To avoid over stroking of the diaphragm, clutch adjustment should be checked and set according to manufacturer’s specification.  Before leaving the production facility all cover assemblies are checked for clamp loading, pressure plate lift and diaphragm run-out utilizing test equipment.

Clutch Plate.

Clutch driven plates can be become distorted during transit or more commonly during installation by ‘hanging’ of the gearbox on the drive shaft.  The risk of distortion can be minimized by the use of an alignment tool and ensuring that the gearbox  is installed without banging on the clutch units.  All driven plates are individually inspected before leaving the factory and tested for run-out and overall consistency of effective thickness using specially designed spin test machines.  In house computerized evaluation equipment is available to measure (in both drive & overrun positions) the torsional damping characteristics of the driven plate.

Release Bearing.

Although it is not possible to fully check the operation of the release bearing when it is removed, it is false economy to re-use the old bearing as this often results is premature clutch failure.  Therefore we recommend that it is always replaced.  Refitment of the old component can also give excessive bearing noise and abnormal diaphragm finger/release lever wear.  The bearing carrier should slide freely on the bearing quill, apply recommended high temperature grease sparingly.

Clutch Cables.

It is recommended that clutch cables are replaced when clutch components are renewed.  Cables often stretch beyond adjust limits resulting in non clearance.  Ensure that the correct cable is fitted and adjusted in accordance with the manufacturer’s specification.

Flywheel.

The flywheel is often ignored during clutch replacement but should always be checked before refitting new clutch components.  Uneven facing wear on the flywheel side of the drive plate can indicate severe flywheel wear, usually observed as a badly grooved mating surface.  Hot spots and thermal cracks indicate the clutch has been running at high temperatures.  Any marking or grooves on the mating surface should be removed or if excessive the flywheel should be replaced.    If the flywheel is to be machined the original overall dimensions must be maintained.  The cover assembly mounting flange must be machined down by the same amount as the contact surface of the flywheel.  The opportunity should be taken to check the flywheel ring gear.

Spigot Bearing/Bush.

The spigot bearing can cause severe damage if worn as it allows the gearbox to ‘float’.  This can result in excessive noise and misalignment leading to damage of the clutch components.  A worn spigot bearing can cause unbalance resulting in vibration.  It is good practice to replace the spigot bearing/bush during clutch replacement.

Engine/Gearbox Oil Seals.

Leaking oils are a major cause of clutch failure, allowing contamination of the clutch components.  A  small amount of contamination will affect the efficient operation of the clutch.  Always check for traces of oil and replace any suspect oil seals.

Release Fork/Release Mechanism.

A substantial amount of the clutch release stroke can be lost if wear on the release mechanism is not corrected.  All parts such as release fork, cross arm, bushes, pivot blocks/pins should be checked and replaced if any wear is located.  Always ensure the free operation of the linkage.

Release Bearing Housing

Wear on the side of the housing can affect the release bearing travel causing grab or chatter of the clutch and off center release bearing contact with the diaphragm.  Ensure that the housing is centered and concentric with the gearbox input shaft.

Engine & Gearbox Mountings.

Worn or damaged parts can cause vibration and shudder, often it is taken for clutch malfunction.  Components showing any signs of wear or damage should be replaced.

Hydraulic Systems.

Inefficient operation of the clutch and non-disengage problems can be caused by old, insufficient or air impregnated hydraulic fluid.  Check operation of hydraulic components such as master and slave cylinders, examine for leaks and replace substandard parts.  Flush the system and bleed after clutch replacement.

Automatic Adjust Mechanisms.

Faulty auto adjust systems can cause excessive clutch slip, diaphragm wear and non engage problems.  When these systems become inefficient it may be possible to replace with a manual adjustment.  Ensure that cables are de-adjusted when new components are fitted and reset to vehicle manufacturer’s specifications.

Clutch Adjustment.

As there are many differing specifications for adjustment always refer to vehicle manufacturers instructions when setting this.  Some vehicles require the release bearing to run in constant light contact with the cover assembly diaphragm, where others demand significant free play.  Overall clutch adjustment is critical in obtaining efficient operation of the clutch, incorrect adjustment can lead to clutch slip, overheating, excessive wear and release carrier contact with the diaphragm.  These faults cause abnormal wear, broken components and premature clutch life.