Component Tests and General Diagnostics

Many noises suspected as coming from the rear axle actually originate from other places such as tires, road surfaces, wheel bearings, engine, transaxle, exhaust system or body drumming. Before disassembling the rear axle, a careful and thorough check is necessary. Also it should be noted that the rear axle gears are not absolutely quiet and that some noise from the rear axle should be accepted as normal. Use the following procedure, to check for axle noise under normal operating conditions.
1. Ensure rear axle lubricant is at proper level.
2. Drive vehicle down a level asphalt road to reduce tire noise and body drumming until rear axle lubricant is thoroughly warm.
3. Note speed that noise is occurring. Stop vehicle and shift transaxle to neutral, run engine slowly up and down through engine speeds, corresponding to vehicle speed where noise was most pronounced, to determine if noise is caused by Exhaust, muffler roar or another engine condition.
4. Separate tire noise from rear axle noise as follows:
a. Tire noise changes with different road surfaces but axle noise does not.
b. Temporarily inflate all tires to 50 psi. If noise is different from before, noise is tire related. If noise is the same as before, noise is probably coming from the rear axle.
c. Rear axle noise usually stops when coasting at speeds under 30 mph. Tire noise will continue, with a lower tone as speed is reduced.
d. Compare noise when pulling to noise when coasting, rear axle noise will usually change, tire noise will remain the same.
e. Check if noise changes with various speeds or sudden acceleration and deceleration. Exhaust and axle noise will usually vary with these conditions, while tire noise will remain the same and is more noticeable at speeds of 20-30 mph.
f. Drive vehicle over smooth pavements or dirt roads (not gravel) with tires at normal pressure. If noise is caused by tires, it will change or disappear and appear again with changes in road surface.
5. Front wheel bearing noise will sometimes be confused with rear axle noise, to check for front wheel bearing noise, proceed as follows:
a. Front wheel bearing noise will remain the same when vehicle is in drive or coasting.
b. Lightly applying the brake pedal while holding vehicle speed constant will often cause front bearing noise to diminish.
c. Raise and support vehicle, then check for front wheel bearing noise by spinning and shaking the front tires.
6. Rear suspension bushings, frame insulators and spring insulators dampen rear axle noise when installed correctly. Ensure that no metal contact exists between spring and spring opening in frame or between upper and lower control arm bushings and rear module. Any metal-to-metal contact may result in telegraphing road noise and normal axle noise.