What is a Pilot Bearing and How Do I Know if Mine is Faulty?
When the clutch is disengaged, the transmission’s input shaft and the engine’s crankshaft are rotating at different speeds. The pilot bearing allows for this difference. This is why a faulty pilot bearing makes its most noise when the clutch pedal is completely depressed and the clutch itself is completely disengaged. It’s located in the center of the crankshaft flange or flywheel.
Pilot bearings are either bearings or bushings. The bearing type can be ball, roller or needle bearings packed in grease. If the manufacturer recommends adding bearing grease, be careful to avoid contaminating the clutch disk or the surface of the flywheel. Pilot bushings are brass and infused with lubrication. Adding lubrication will actually increase friction with these soft metal type bushings. Check with the vehicle manufacturer’s recommendations before adding any lubrication to a pilot bearing.
Diagnosing a Faulty Pilot Bearing
A worn or damaged pilot bearing will make a whining or grinding noise. It will be very loud if the bearing is completely damaged. It occurs whenever the crankshaft and input shaft are rotating at different speeds. A clutch release bearing is different; it will make a chirping or squealing noise as soon as the bearing touches the pressure plate’s diaphragm. Note that release bearings make noise with much less pedal travel.
Most rear wheel drive, and some front wheel drive, vehicles with manual transmissions use a pilot bearing/bushing. The pilot bearing/bushing supports and centres the transmission input shaft and clutch disc. When the clutch is disengaged, the pilot bearing/bushing allows the flywheel to maintain engine RPM while the input shaft is slowing down and stopping.
Types of pilot bearing/bushing include conventional ball bearings, needle bearings and sintered bronze bushings.
When a pilot bearing/bushing fails, a vehicle may exhibit:
- No release;
- The transmission may pop out of gear;
- Vibration; and
- Catastrophic failure of the transmission if not fixed
Early signs of the pilot failing may be noise whenever the clutch is disengaged. The driver may also notice that the transmission is difficult to shift between gears or hard to put into reverse or first gear when stopped.
When the pilot is failing, or has failed, the input shaft will be allowed to walk around causing it to go off centre. When this happens, the transmission input shaft will begin moving around inside the transmission causing the gears and synchronizers to be off centre resulting in the transmission popping out of gear.
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