Clutch Slave Cylinder
A hydraulic cylinder that receives fluid pressure from the clutch master cylinder to physically push and disengage the manual transmission clutch.
The clutch slave cylinder is a key actuator in a manual transmission's hydraulic clutch system. When the driver presses the clutch pedal, the clutch master cylinder forces hydraulic fluid down a line into the slave cylinder. The pressurized fluid pushes a piston inside the slave cylinder, extending a pushrod that presses against the clutch fork or release bearing, disengaging the clutch from the engine.
In many modern vehicles, the slave cylinder is integrated with the release bearing as a single concentric unit (CSC) mounted inside the transmission bellhousing. Failures occur when the internal rubber seals leak, causing fluid loss, a spongy clutch pedal, or a clutch that fails to disengage (preventing gear shifts).
Replacing a concentric slave cylinder requires removing the transmission, so mechanics highly recommend replacing the clutch disc, pressure plate, and pilot bearing at the same time.