Operators of commercial vehicles fear nothing more than long downtimes due to repairs. If the clutch system is defective expensive and lengthy work may be necessary. With one exception: Repairs of the release system can be done relatively quickly – especially with the Sachs complete kits by ZF Aftermarket.
Clutches of commercial vehicles are subject to heavy loads. The use of the release fork with every clutch actuation leads to heavy wear on the fork, shaft and bearing. In the long term, this can result in a one-sided clutch actuation or not completely reaching the release path. Consequences can include increased bearing wear or shifting problems. The correct function of the release system is also essential for the fault-free operation of automated manual transmissions such as ZF's AS Tronic.
Malfunctions can lead to long downtimes and thus to high costs. For this reason, CV workshops should make their customers aware to visit the workshop at the first sign of such malfunctions. If problems with the release system are the cause, they can be repaired relatively quickly and inexpensively, this way the described consequential damage can be prevented in the first place.
The experts at ZF Aftermarket differentiate between two basic types of damage in the release system:
1. Off-center alignment of the clutch release bearing:
Bent or worn guide sleeves or release forks lead to off-center alignment and thus to an uneven actuation of the diaphragm spring. The result is a disproportionate abrasion at the contact point between the diaphragm spring and the pressure plate (roof slope). Due to the worn roof pitch of the pressure plate, the axial position of the membrane spring changes. The pedal force is then no longer sufficient, resulting in a slipping clutch. The premature failure of the release and clutch is thus inevitable.
2. Worn components in the release system:
Wear on the actuating mechanism requires increased pedal force in the long term. Special attention must be paid to:
If any of these indicate advanced stages of wear, are dry, bent, worn or broken, the mechanism becomes stiff. Clutch grab, separation difficulties or a sluggishness in the clutch are the consequences. Due to the lack of release force, a manual movement check of the release shaft is not enough. Only a visual inspection allows a clear assessment.
When repairing it is important to work according to the assembly instructions to avoid tilting the release fork. The first sign of wear can be a difficult operation of the clutch. In addition, the release path is shortened and separation difficulties may occur. Due to the tilting, the force of the diaphragm spring is no longer effective and the clutch starts to slip after a short running time.
Release forks in original equipment quality
As an OE supplier, ZF also provides release forks in original equipment quality into the aftermarket. One of the largest product ranges is available to the replacement market under the Sachs brand. The Schweinfurt/Germany-based company can supply spare parts for more than half of the world’s commercial vehicle parc. The range includes output forks for ZF's own transmissions but also for third-party brands. Spare parts kits containing all necessary components such as shafts, seals, or screws may be particularly interesting for CV workshops. These can help saving time for the workshop when it comes to selecting and ordering parts but also avoid the risk of delays in repairs due to missing components.