Many noises that are reported as coming from the rear axle actually originate from other components.

Any of the following components may be the source of noises that are reported as coming from the rear axle:

Thoroughly inspect for the source of the noise before disassembling the rear axle. Noise that originates in other places cannot be corrected by adjustment or replacement of rear axle components. Rear axle differential gears are not absolutely quiet (like any other mechanical devices). Rear axle differential gears should be accepted as commercially quiet unless some abnormal noise exists.

Use the following procedure in order to inspect for axle noise under standard conditions:

1. Measure the rear axle lubricant in order to ensure the correct level.
2. Drive the vehicle far enough in order to thoroughly warm up the rear axle lubricant.

Select a level asphalt road. A level asphalt road will reduce tire noise and body drumming.

3. Note the speed at which the noise occurs.
4. Stop the vehicle.
5. Determine if the exhaust muffler roar or other engine conditions cause the noise:

5.1.	Place the transmission range selector lever in NEUTRAL

5.2.	Run the engine slowly up and down through the engine speeds that correspond to the speed at which the noise was most pronounced.

6. Determine if the tires cause the noise:

•	Temporarily inflate all of the tires to approximately 345 kpa (50 psi).

•	This will alter the noise caused by the tires, but will not affect the noise made by the rear axle.

•	Test drive the vehicle. Coast at speeds under 48 km/h (30 mph).

•	The following characteristics of tire and rear axle noise may help in determining if the tires cause the noise:

•	Rear axle noise usually stops when the vehicle is coasting at speeds under 48 km/h (30 mph).

•	Tire noise usually continues. The tone of the tire noise becomes lower as the speed of the vehicle is reduced.

•	Rear axle noise usually sounds different during driving and during coasting. Tire noise remains the same during driving and during coasting.

•	Exhaust and axle noises change during sudden acceleration and deceleration. Tire noise remains constant during sudden changes in vehicle speed.

•	Tire noise is the most noticeable at the speeds of 32 to 48 km/h (20 to 30 mph).

•	Tire noises changes on different road surfaces, but rear axle noise does not. Drive the vehicle over smooth pavement or dirt roads (not gravel) with the tires at normal pressure. If the noise is caused by the tires, it will noticeably change or disappear and reappear with the road surface.

7. Determine if loose or rough front wheel inner or outer bearings cause the noise.

The following characteristics of noise caused by loose or rough front wheel inner or outer bearings may help in determining if loose or rough bearings cause the noise:

Loose or rough front wheel inner or outer bearings will cause a noise which may be confused with rear axle noise. Noise in the above components does not change when comparing drive and coast. the noise in the above components to diminish. Applying the brake pedal while holding the speed constant removes some of the weight off the bearing. Use the following procedure in order to test the front inner and outer bearings for noise:

•	Noise in front wheel inner or outer bearings does not change between drive and coast.

•	Light application of the brake pedal while holding the vehicle speed steady takes some weight off of the bearings. This action will often cause noise in front wheel inner or outer bearings to diminish.

•	Use the following steps in order to determine if the front wheel inner and outer bearings are loose:

1.	Jack up the tires and the wheels.

2.	Spin or shake the tires and the wheels in order to determine if the bearings are loose.

8. Rear axle noise is dampened when the rear suspension rubber bushings and the spring insulators are correctly installed.

Determine if any metallic contact exists between the following components:

•	The spring and the spring opening in the underbody

•	The lower control arm bushings and the underbody or axle housing brackets

•	Metal-to-metal contact at these points may increase road noise and normal axle noise.

After verifying that a noise exists in the rear axle, determine the type of the noise. Determining the type of the rear axle noise will aid in repair.

Gear noise (whine) is audible from 32-89 km/h (20- 55 mph) under the following driving conditions:

Poor bearings generally produce a rough growl or grating sound, rather than the whine typical of gear noise.

Bearing noise frequently "wow-wows" at constant RPMs. This noise may indicate that the following components are faulty:

The "wow-wow" bearing noise may be confused with rear wheel bearing noise. Inspect and replace as necessary.

The noise that is produced by a rough rear wheel bearing is evident under the following conditions:

The bearing noise may diminish with gentle braking.

Use the following steps in order to determine if a noise is caused by a rough rear wheel bearing:

1. Raise the rear tires and wheels.
2. Spin the rear tires and wheel by hand.
3. Listen at the hubs for evidence of rough (noisy) rear wheel bearings.

One of the following conditions may cause a knock at low speeds:

Inspect and replace the above components as necessary.

One of the following conditions may cause excessive backlash clunk with acceleration and deceleration:

Replace the worn components as necessary. Select close fitting replacement parts.

Adjust the differential ring gear-to-differential drive pinion gear backlash. Refer to Backlash Adjustment