The clutch assembly consists of a clutch disc, a clutch pressure plate, and a clutch release bearing. All these components are usually replaced at the same time. The clutch assembly has two key functions: it transmits power produced by the engine to the gearbox, and it allows that power to be interrupted when the clutch pedal is depressed. Power produced by the engine requires this interruption. It makes it possible to change gears and to shift into neutral at a traffic light or stop sign.
When the clutch assembly is not operating correctly, two things can happen. It either doesn't interrupt the power from the engine to the gearbox, which causes grinding sounds and difficulty in selecting gears. Or it fails to transmit the drive from the engine to the gearbox. This results in the engine “revving up” without the vehicle speed increasing. In the case of a complete failure, the engine will rev up, but the vehicle will not move. Clutch components naturally wear out. Clutch components may fail or wear due to; bad driving habits, being driven with the clutch improperly adjusted, or from exposure to oil.
To replace the clutch assembly, the driveshaft (or half shafts where applicable) and the manual transmission (gearbox) must be removed to gain access to the clutch components. New clutch components are fitted and the gearbox is then reinstalled.