Bearing

What's a Throwout Bearing? We Tell You Here!
Technically speaking, the correct terminology for a throwout bearing is release bearing, as in clutch release bearing. When considered in those terms, it's easier to imagine what this component is and what it does. The throwout bearing is the last piece in the series of components that composes the clutch linkage from the pedal to the clutch assembly inside the transmission bellhousing.

It's a bearing, meaning that it allows interaction between a moving surface and a stationary surface. Just like wheel bearings allow movement of the spinning wheel hub around the non-moving spindle, the throwout bearing is the component that comes between the clutch pressure plate, which is spinning when the engine is running, and the non-moving clutch fork- or the hydraulic slave cylinder typically found in newer cars. Although there are a few different ways a clutch can be actuated, mechanical or hydraulic, the function of the throwout bearing is the same. It connects moving and non-moving parts.


The throwout bearing is made up of a base, which is attached to the linkage assembly, the outer shell that pushes against the pressure plate, and the bearing assembly located between the two.

In a clutch assembly, the pressure plate is bolted to the flywheel and is rotating any time the engine is running. The friction disc slips over the splines of the transmission's input shaft and only turns when the drive wheels are turning.

The release bearing is held by the stationary clutch fork and, when the clutch pedal is pressed, pivots forward to contact the diaphragm spring of the pressure plate, which act like a lever to disengage the clutch, separating the mechanical link between the engine and the transmission's input shaft.

Clutch linkages are either mechanical or hydraulic. Hydraulic clutch systems will have either an external slave cylinder or an internal slave cylinder. Mechanical systems include actuating rods and a bellcrank, commonly referred to as a Z-bar, or via a cable between the pedal and clutch fork.

Most cars made since the late '90s have hydraulic clutch systems with an internal slave cylinder, meaning the slave cylinder is located inside the transmission bellhousing.