For 1990-2009 cars

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

• | The tires and wheels

• | The road surfaces

• | The wheel bearings

• | The engine

• | The transmission

• | The muffler

• | The body

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. The rear axle differential gears are not absolutely quiet (like any other mechanical devices). The 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, which reduces 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:

6.1. | 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.

6.2. | 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 32-48 km/h (20-30 mph).

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

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

### Rear Axle Noises

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

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

• | Drive -- Acceleration or heavy pull

• | Road Load -- The vehicle driving load or the constant speed

• | Float -- Using enough throttle in order to keep the vehicle from driving the engine, the vehicle slows down gradually but the engine still pulls slightly.

• | Coast -- The throttle closes and the vehicle is in gear.

| Gear noise is most noticeable when the vehicle is operating at the following speeds:

- | 64-80 km/h (40-50 mph)

- | 97-105 km/h (60-65 mph)

### Bearing Noise

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 differential drive pinion gear

• | The side bearings

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

### Rear Wheel Bearing Noise

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

• | The vehicle is coasting at low speeds

• | The transmission range selector lever is in NEUTRAL

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.

### Knock At Low Speeds

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

• | A worn universal joint

• | A worn or oversized side gear hub counterbore in the differential case

Inspect and replace the above components as necessary.

### Backlash Clunk

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

• | A worn differential drive pinion gear shaft

• | A worn differential case

• | Excessive clearance between the following components:

- | The rear axle shaft splines and the side gear splines

- | The side gear hub and the counterbore in the case

• | A worn differential drive pinion gear and worn side gear teeth

• | Worn differential pinion gear thrust washers

• | Excessive differential ring gear-to-differential drive pinion gear backlash

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