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SACHS useful tip:

Identifying faults in the release system.

Specialized knowledge helps prevent damage

Many clutch deficiencies in commercial vehicles can be traced to the influence of faulty release systems. These deficiencies also include "capital" failures such as burnt-out clutches or poor disengagement performance, for which one might not initially suspect the release system. Therefore a precise inspection is very important. There are not many maintenance jobs where concentrating on a few details can have such a big effect and save major costs.

Three examples should serve to explain the types of damage that can result from a deficient release system:

SACHS release system

Specialized knowledge helps prevent damage

Many clutch deficiencies in commercial vehicles can be traced to the influence of faulty release systems. These deficiencies also include "capital" failures such as burnt-out clutches or poor disengagement performance, for which one might not initially suspect the release system. Therefore a precise inspection is very important. There are not many maintenance jobs where concentrating on a few details can have such a big effect and save major costs.

Three examples should serve to explain the types of damage that can result from a deficient release system:

SACHS release system

Types of damage

Wear

If the bearing points of the guide sleeve (shown in this picture), the release fork, or the release shaft are worn, this compromises the clutch's ease of movement – the worst case scenario is a total clutch failure.

Wear

If the bearing points of the guide sleeve (shown in this picture), the release fork, or the release shaft are worn, this compromises the clutch's ease of movement – the worst case scenario is a total clutch failure.

Eccentricity

If, as a result of worn components, the release bearing is no longer guided precisely, this also causes an eccentric movement of the diaphragm spring. This in turn leads to considerable abrasion in the contact line (pitch) of the pressure plate. The axial position of the diaphragm spring is modified as a consequence, leads to a reduced frictional connection, and thus makes the clutch slip.

Eccentricity

If, as a result of worn components, the release bearing is no longer guided precisely, this also causes an eccentric movement of the diaphragm spring. This in turn leads to considerable abrasion in the contact line (pitch) of the pressure plate. The axial position of the diaphragm spring is modified as a consequence, leads to a reduced frictional connection, and thus makes the clutch slip.

Wrong position

A release bearing which was incorrectly "threaded", i.e. incorrectly positioned, during assembly, will get stuck in the fork. To begin with, this results in a stiff clutch, the release distance becomes shorter, and the clutch is not separated properly. The stuck fork does not transfer the force of the diaphragm spring effectively. After a short runtime, the clutch will also start slipping.

Wrong position

A release bearing which was incorrectly "threaded", i.e. incorrectly positioned, during assembly, will get stuck in the fork. To begin with, this results in a stiff clutch, the release distance becomes shorter, and the clutch is not separated properly. The stuck fork does not transfer the force of the diaphragm spring effectively. After a short runtime, the clutch will also start slipping.

Worn components in the release system

Wear in the release mechanism is one reason for increased pedal forces. Particular attention must be paid to the following:

  • the contact surfaces of the release fork,
  • the contact surfaces of the release shaft,
  • the release fork itself.

If these have entered advanced stages of wear, as is shown in the photo with worn guiding sleeve, are dry, worn, or broken, this will have negative consequences on shift performance. Consequences include grab, drag, or an increasing degree of sluggishness in the clutch. Because there is no load on the release system, manual testing of release shaft operation is not effective. Here a visual inspection is required.

Worn components in the release system

Wear in the release mechanism is one reason for increased pedal forces. Particular attention must be paid to the following:

  • the contact surfaces of the release fork,
  • the contact surfaces of the release shaft,
  • the release fork itself.

If these have entered advanced stages of wear, as is shown in the photo with worn guiding sleeve, are dry, worn, or broken, this will have negative consequences on shift performance. Consequences include grab, drag, or an increasing degree of sluggishness in the clutch. Because there is no load on the release system, manual testing of release shaft operation is not effective. Here a visual inspection is required.

ZF Aftermarket products

Clutch parts as kit

ZF Aftermarket offers clutch parts as complete kits for easy service which include clutch pressure plate, clutch disk, and release bearing. All ZF Aftermarekt kits include a matching grease pad with high-performance lubricant for one-time, professional greasing of the hub splines during installation.

Release forks for commercial vehicles

Clutch release forks for commercial vehicles are also new additions to the product range. ZF Aftermarket delivers them ready for assembly in one kit.

Further information