Clutch Release Bearing
The clutch release or throwout bearing contains a collared bearing that spins along with the spinning pressure plate as the clutch pedal is depressed. A worn release bearing makes a squealing or growling sound heard from the transmissions clutch housing when the clutch pedal is depressed.
Most of today's manual transmissions have hydraulic clutch circuits. Still, many have mechanical linkage; they use rods and cables to control the clutch. They have constant running bearings that spin whenever the engine is running and must be adjusted to maintain a slight preload after installation.
Typically, the clutch release bearing and pressure plate are replaced while replacing a worn clutch friction disc. The engine and transmission must be separated to replace the bearing.
A throwout bearing begins to growl as it wears or loses lubrication. It is usually necessary to lubricate the shaft the bearing rides on during assembly. Check in the manufacturer's manual for assembly specifications.
Listen for a chirping sound as the clutch pedal is first depressed. This sound is the worn (un-lubricated) release bearing contacting the fingers of the pressure plate's diaphragm. These fingers can also wear, causing similar noise-related issues.