Axle Noise

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

The noises described as follows usually have specific causes that can be diagnosed by observation as the unit is disassembled. The initial clues are the type of noise heard during the road test.

Gear Howl and Whine
Howling or whining of the ring gear and pinion is due to an improper gear pattern, gear damage or improper bearing preload.

Bearing Whine
Bearing whine is a high-pitched sound similar to a whistle. It is usually caused by worn/damaged pinion bearings, which are operating at driveshaft speed. Bearing noise occurs at all driving speeds. This distinguishes it from gear whine which usually comes and goes as speed changes.
As noted, pinion bearings make a high-pitched, whistling noise, usually at all speeds. If however, there is only one pinion bearing that is worn/damaged, the noise may vary in different driving phases. Pinion bearings must not be replaced unless they are scored or damaged or there is a specific pinion bearing noise. A worn/damaged bearing will normally be obvious at disassembly. Examine the large end of the rollers for wear. If the pinion bearings original blend radius has worn to a sharp edge, the pinion bearing must be replaced.

NOTE: A low-pitched rumble normally associated with a worn/damaged wheel bearing can be caused by the exterior luggage rack or tires.

A wheel bearing noise can be mistaken nor a pinion bearing noise. Check the wheel bearing for a spalled cup, and spalled/damaged rollers. Replace the wheel bearing if any of these concerns are detected.

Chuckle





Chuckle that occurs on the coast driving phase is usually caused by excessive clearance between the, differential gear hub and the differential case bore.
Damage to a gear tooth on the coast side can cause a noise identical to a chuckle. A very small tooth nick or ridge on the edge of a tooth can cause the noise.
Clean the gear tooth nick or ridge with a small grinding wheel. If the damaged area is larger than 3.2 mm (1/8 inch), replace the gearset.
To check the ring gear and pinion, remove as much lubricant as possible from the gears with clean solvent. Wipe the gears dry or blow them dry with compressed air. Look for scored or damaged teeth. Also look for cracks or other damage.
If either gear is scored or damaged badly, the ring gear and pinion must be replaced.





If metal has broken loose, the axle housing must be cleaned to remove particles that will cause damage. At this time, any other damaged parts in the axle housing must also be replaced.

Knock
Knock, which can occur on all driving phases, has several causes including damaged teeth or gearset.





A gear tooth damaged on the drive side is a common cause of the knock. This can usually be corrected by grinding the damaged area.

Clunk





Clunk is a metallic noise heard when the automatic transmission is engaged in REVERSE or DRIVE. The noise may also occur when throttle is applied or released. It is caused by backlash somewhere in the driveline or loose suspension components; it is felt or heard in the axle. Refer to Total Backlash Check.
Additionally, clunk may be heard upon initial drive-away. This occurs as engine torque shifts vehicle weight, forcing changes in driveline angles, preventing the driveshaft slip-yoke from sliding on the output shaft. To correct for this condition, lubricate the slip-yoke splines.

Total Backlash Check
1. Raise and support the vehicle.
2. Remove the driveshaft.
3. Install the Companion Flange Holding Tool.





^ Clamp a rigid bar or pipe to the tool. Clamp the other end of the bar or pipe to the frame or a body member in order to prevent movement of the rear axle companion flange.

4. Lower the vehicle so that one rear wheel is resting on a wheel chock to prevent it from turning. The other rear wheel will be used to measure total rear axle backlash.
5. Rotate the free wheel slowly, by hand, until the feeling of driving the rear axle is encountered. Place a mark on the side of the tire, 305 mm (12 inches) from the center of the wheel, with a crayon or chalk.
6. While holding the crayon or chalk against the tire, rotate the wheel slowly in the opposite direction until the feeling of driving the rear axle is encountered again.
7. Measure the length of the crayon or chalk mark on the tire.
^ If the length of the mark is 25.4 mm (1 inch) or less, the rear axle backlash is within allowable limits.
^ If the chalk mark is greater than 25.4 mm (1 inch), check for these conditions:
- Elongation of the differential pinion shaft and holes in the differential case.
- Missing differential pinion thrust washer or differential side gear thrust washer.
- Galling of the differential pinion shaft and bore.
- Excessive ring gear and pinion backlash. Follow the procedure for the type of rear axle to check backlash.

Bearing Rumble
Bearing rumble sounds like marbles being tumbled. This condition is usually caused by worn/damaged wheel bearing. The lower pitch is because the wheel bearing turns at only about one-third of the driveshaft speed. Wheel bearing noise also may be high-pitched, similar to gear noise, but will be evident in all four driving modes.