Rear Hub Bearing

Axle Pitch Line Runout and/or Boom
This condition can be misdiagnosed as driveline imbalance. The symptoms are very similar: vibration and/or boom in the 72-97 kph (45-60 mph) range. It is important to test carefully.

Driveline imbalance yields a vibration and/or boom that is present in all modes of operation: drive, coast and neutral coast. Axle pitch line runout symptoms may change between drive and coast because the pitch line runout can be different on the drive side and coast side of the gear teeth and will definitely improve in neutral coast where the gears are unloaded.

If the source of the problem is high pitch line runout, it is necessary to change the ring and pinion gears as a set.






Hub Bearing - Rear
Bearing malfunctions normally will be obvious at disassembly. Pinion bearings make a high-pitched, whistling noise, usually at all speeds. However, if there is only one pinion bearing that is malfunctioning, the noise may vary in different driving phases.

If bearing cup is spalled (A) or bearing roller(s) are spalled (B), replace the bearing. Pinion bearings are frequently replaced unnecessarily when correcting gear noise. They should not be replaced unless they are actually scored or damaged, or there is a specific pinion bearing noise. Examine the large end of the rollers for wear. If the original blend radius has worn to a sharp edge, the bearing assembly must be replaced.

Remember that the low-pitched rumble of a malfunctioning wheel bearing can be duplicated by a wind noise from externally mounted accessories or by tires.






On semi-floating type axles, wheel bearing noise might be mistaken for pinion bearing noise, so make sure to look at the wheel bearings carefully before disassembling the axle.

Wheel bearings on semi-floating type axles are pressed into the housing at the axle tube ends. The axle shaft is the inner race for the bearing. The rollers run approximately on the center of the polished surface. So if the bearing is damaged, the roller surface on the shaft will be damaged as well.