Rear Drive Axle Noises

Rear Drive Axle Noises
Gear Noise

Gear noise or whine is audible from 32 - 89 km/h (20 - 55 mph) under 4 driving conditions:
^ Drive- Acceleration or heavy pull
^ Road Load-Vehicle driving load or constant speed
^ Float-Using enough throttle to keep the vehicle from driving the engine, the vehicle slows down gradually but the engine still pulls slightly
^ Coast-Throttle is closed and the vehicle is in gear

Gear noise most frequently has periods where the noise is more prominent, usually between 48 - 64 km/h (30 - 40 mph) and 80 - 85 km/h (50 - 53 mph). Gear whine is corrected by either ring and pinion gear replacement or adjustment, depending on the mileage of the gearset.

Bearing Noise
Faulty bearings produce a rough growl or grating sound, rather than the whine typical of gear noise. Bearing noise/hum will pulsate at a constant vehicle speed. This indicates a bad pinion or a bad rear axle side bearing. This noise can be confused with rear wheel bearing noise. Inspect and replace the bearings and the affected components as required.

Rear Wheel Bearing Noise
A rough rear wheel bearing produces a noise which continues with the car coasting at low speed and the transmission in neutral. The noise may diminish some when the brakes are gently applied. The noise may also change when performing side-to-side maneuvers with the vehicle.

A rough/noisy rear wheel bearing can be heard by spinning the rear wheels by hand and listening at the hubs for the noise. Inspect and replace the bearings and the affected components as needed.

Knock at Low Speeds
A low speed knock can be caused by a differential case side gear bore that has worn oversize. Inspect the side gears and differential case and replace the components as necessary.

Backlash Clunk
Excessive backlash clunk under acceleration or deacceleration can be caused by any of the following:
^ Worn differential pinion shaft
^ Worn differential pinion and/or side gear teeth
^ Worn thrust washers
^ Excessive clearance between the side gears and the axle shafts
^ Excessive clearance between differential side gears and the bore in the case
^ Excessive drive pinion and ring gear backlash

Inspect, adjust or replace the affected components as necessary.