Bearing Rumble

- Bearing rumble sounds like marbles being tumbled. This condition is usually caused by a damaged pilot bearing. The lower pitch is because the pilot bearing turns at only about one-third of driveshaft speed.
- Bearing damage will normally be obvious at disassembly. As noted earlier, damaged 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.
- Pinion bearings are frequently replaced unnecessarily on axles with mileage under 24,139 km (15,000 miles) 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 bearing's original blend radius has worn to a sharp edge, the differential pinion bearing should be replaced.