Gear Howl and Whine

Before disassembling the axle to diagnose and correct gear noise, eliminate the tires, exhaust, trim items, roof racks, axle shafts and rear wheel bearings as possible causes.

The noises described under Road Test usually have specific causes that can be diagnosed by observation as the unit is disassembled. The initial clues are the type of noise heard on the road test and the driving conditions.

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

Differential pinion bearings are frequently replaced unnecessarily on axles with low 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 differential pinion bearing noise. Examine the large end of the rollers for wear. If the differential pinion bearings original blend radius has worn to a sharp edge, the differential pinion bearing must be replaced.

Remember that the low-pitched rumble of a malfunctioning wheel bearing can also be caused by the exterior luggage rack or tires.





Rear wheel bearing noise can be mistaken for pinion bearing noise. Look at the rear wheel bearing carefully before tearing down the axle. Check for a spelled cup, spelled roller or damaged rollers. Replace the rear wheel bearing if any of these concerns are detected.





Rear wheel bearings are pressed into the axle housing tubes, making them more difficult to check. However, the axle shaft is the inner race for the bearing. If the bearing is damaged, the roller surface on the axle shaft can also be damaged. The rollers run approximately on the center of the polished surface.