Clutch assemblies are used for manual transmissions to be shifted through a set of gears without damaging the transmission or gear sets. It is mounted to the engine's flywheel, and the transmission's input shaft is locked into the clutch disc. This provides the clutch the opportunity to lock the engine to the transmission, and transfer power from the engine to the transmission.
How do Clutch Assemblies work?
When the clutch is engaged - clutch pedal not pressed - a large spring pressure the pressure plate into the clutch disc, which is then pressed into the flywheel. This causes the engine flywheel to turn the transmission input shaft at engine speed. When the clutch pedal is pressed, the clutch disc, flywheel, and pressure plate are no longer pressed together. This allows the clutch pressure plate and flywheel to rotate independent of the the clutch disk. Since the clutch disc is connected to the transmission input shaft, the transmission input shaft will slow down quickly to allow shifting.
When does the Clutch Assembly need Adjustment?
If the clutch is unadjusted, one of two things will happen. The clutch could fail to engage and slip while the clutch pedal is not pressed, or the clutch could fail to fully disengage when the clutch pedal is pressed to the floor. In both situations, clutch material will likely be burned off, and the driver and passengers will smell the clutch friction material burning off at some point. Also, after extended use of an unadjusted clutch, the clutch may fail entirely, and the transmission can no longer be locked to the engine.
Can I drive with an unadjusted clutch?
The clutch is expensive to replace but cheap to adjust. For this reason alone, the vehicle should be brought in for inspection as soon as issues arise. Also, since normal operation of the clutch is typically necessary to operate a vehicle, the vehicle will likely be useless until repaired or adjusted.
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How often should the Clutch System need Adjustment?
Clutches fail or need adjustment all the time. For drivers well versed in driving manual transmissions, especially for light vehicles, the clutch can last the life of the vehicle. However, if the vehicle is used to learn how to drive a manual transmission, hauls heavy loads, is quite large, is driven with a foot rested on the clutch pedal, or is driven in hilly terrain, the clutch may only last 50,000 - 75,000 miles before adjustment or replacement.
How is the Clutch System Diagnosed?
Diagnosis of a clutch is as simple as attempting to drive the vehicle. If the clutch is slightly disengaged without pressing the clutch pedal, slightly engaged while pressing the clutch pedal to the floor, or does not engage or disengage under any circumstances, it will be adjusted. If adjustment fails to remedy the situation, the clutch will be replaced.
How is the Clutch Assembly Adjusted?
Adjusting the clutch is most typical for cable type clutches, and the cable will be adjusted by changing the length of the cable on the clutch fork. This can be done with shims or an adjusting nut. Hydraulic clutches have some adjustment at the clutch pedal, and many can be adjusted by turning an adjusting screw and pinch-nut on the slave cylinder or moving the slave cylinder in eccentric holes. However, in some cases, changing the pushrod for the slave cylinder is necessary for adjustment, and this is typically not performed.
RepairPal Recommendations for Clutch Assembly issues
We recommend having any vehicle with clutch issues towed instead of driven to the repair facility. Clutch issues become much more expensive if the clutch is allowed to wear due to adjustment, but adjustment is typically a fast and economical repair. Also, we recommend having the flywheel replaced or resurfaced when replacing the clutch. This will limit slippage of the new clutch by ensuring maximum friction and contact between the clutch disc and the flywheel.
What to look out for when dealing with Clutch System issues
If the vehicle uses a hydraulic clutch, a small leak in the hydraulic clutch master cylinder, line, or slave cylinder will cause the same symptoms as a clutch which is out of adjustment. Ensure the system is leak free before attempting to adjust the system. Some cable type clutches adjust at the clutch pedal or firewall instead of the clutch fork, so locating the components of the clutch system is necessary. Lastly, if the clutch is unadjustable or self adjusting, yet the clutch begins to give failure symptoms, the clutch should be replaced.
Can I adjust the Clutch Assembly?
The advanced DIY mechanic can adjust the clutch with no problem, however, if proper procedure is not followed or there is a lack of experience or knowledge of the clutch assembly, the repair or adjustment should be left to a professional technician. This may help prevent premature clutch failure and unpredictable clutch performance.
GMC Clutch Assembly Adjust Cost Estimates
The average cost for a Clutch Assembly Adjust is between $61 and $90 but can vary from car to car.