Pilot Bearing
A small bearing or bushing in the crankshaft flange that supports the tip of the transmission input shaft.
A pilot bearing (or pilot bushing) is a small roller bearing or brass bushing pressed into the center of the engine's crankshaft flange. Its primary purpose is to support and align the tip of the transmission's input shaft where it extends through the clutch disc. Because the input shaft spins independently of the crankshaft when the clutch pedal is depressed, the pilot bearing allows the shaft to rotate smoothly relative to the engine.
Over time, the grease inside a pilot bearing can dry out, or the bearing rollers can wear down, leading to mechanical play and friction. A failing pilot bearing typically makes a whirring, squealing, or grinding noise when the clutch pedal is fully depressed, which disappears when the pedal is released.
If it seizes, it can prevent the transmission input shaft from stopping, making it very difficult to shift gears into first or reverse. Replacing the pilot bearing is a standard recommendation whenever a clutch replacement is performed.