Noise Diagnostic Procedures

Noise Diagnostic Procedure

Non-Axle Noise
The five most important sources of non-axle noise are exhaust, tires, roof racks, trim and mouldings, and transmission.

Therefore, make sure that none of the following conditions are the cause of the noise before proceeding with a driveline teardown and diagnosis.
- In certain conditions, the pitch of the exhaust may sound very much like gear noise. At other times, it can be mistaken for a wheel bearing rumble.
- Tires, especially snow tires, can have a high pitched tread whine or roar, similar to gear noise. Radial tires, to some degree, have this characteristic. Also, any non-standard tire with an unusual tread construction may emit a roar or whine type noise.
- Trim and mouldings can also cause whistling or a whining noise.
- Clunk may be a metallic noise heard when the automatic transmission is engaged in reverse or drive, or it may occur when the throttle is applied or released. It is caused by backlash somewhere in the driveline.
- Bearing rumble sounds like marbles being tumbled. This condition is usually caused by a damaged wheel bearing.

Noise Conditions
- Gear noise is typically a howling or whining due to gear damage or incorrect bearing preload. It can occur at various speeds and driving conditions, or it can be continuous.
- Chuckle is a particular rattling noise that sounds like a stick against the spokes of a spinning bicycle wheel. It occurs while decelerating from 64 km/h (40 mph) and can usually be heard all the way to a stop. The frequency varies with vehicle speed.
- Knock is very similar to chuckle, though it may be louder and occurs on acceleration or deceleration. The teardown will disclose what has to be corrected.

Check and rule out tires, exhaust and trim items before disassembling the transmission to diagnose and correct gear noise.

The noises described under Road Test usually have specific causes that can be diagnosed by observation as the unit is disassembled. The initial clues are the type of noise heard on the road test and the driving conditions.

Vibration Conditions

NOTE: New constant velocity (CV) joints should not be installed unless disassembly and inspection revealed unusual wear.

Clicking, popping or grinding noises may be caused by the following:
- cut or damaged drive half shaft joint boots resulting in inadequate or contaminated lube in the outboard or inboard CV joint bearing housings
- loose drive half shaft joint boot clamps
- another component contacting the drive half shaft
- worn, damaged or incorrectly installed wheel bearing, suspension or brake component

Vibration at highway speeds may be caused by the following:
- out-of-balance front or rear wheels
- out-of-round tires
- driveline imbalance
- driveline run-out (alignment)

NOTE: Drive half shafts are not balanced and do not contribute to rotational vibration disturbances.

Shudder or vibration during acceleration may be caused by the following:
- Excessively worn or damaged outboard or inboard CV joint shaft pilot bearing housing
- Excessively high CV joint operating angles caused by incorrect ride height. Check ride height, verify correct spring rate and check items under Inoperative Conditions

Leakage Conditions
1. Inspect the CV joint boots for evidence of cracks, tears or splits.
2. Inspect the underbody for any indication of grease splatter in the vicinity of the front or rear wheel drive half shaft joints and boots. If any grease is present this indicates damage to the half shaft joint boot or boot clamp.
3. Inspect the inboard CV joint stub shaft pilot bearing housing seal for leakage at the inboard CV joint pilot bearing housing.

Inoperative Conditions
- If a CV joint or half shaft pull-out occurs, check the following:
- suspension components for correct location, damage or wear bushings for wear
- subframe for damage
- bent or worn components: stabilizer bar link left-hand rear suspension lower arm and bushing right-hand rear suspension lower arm and bushing rear wheel hub and half shaft left-hand front suspension lower arm and bushing right-hand front suspension lower arm and bushing front wheel hub and half shaft.