Axle Noise

NOTE: A gear-driven unit, especially an automotive drive axle will produce a certain amount of noise. Some noise is acceptable and may be audible at certain speeds or under various driving conditions, for example, on a newly-paved blacktop road. Slight noise is not detrimental to operation of the rear axle and is considered normal.

DESCRIPTION
The following is a glossary of axle noise terms:
^ Gear noise is the typical howling or whining of the ring gear and pinion. 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 the speed of the vehicle.
^ 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.
^ Clunk may be a metallic noise heard when the automatic transmission is engaged in REVERSE or DRIVE, or it may occur when throttle is applied or released. It is caused by backlash somewhere in the driveling or loose suspension components. It is felt or heard in the axle.

NON-AXLE NOISE
There are a few other conditions that may sound like axle noise and must be considered in pre-diagnosis. The most common are exhaust, tires and trim moldings.
^ In certain conditions, the pitch of the exhaust may sound very much like gear whine. 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. Any non-standard tire with an unusual tread construction may also emit a roar or whine-type noise.
^ Trim, grille and moldings can also cause whistling or whining noises.
Make sure none of these is the cause of the noise before proceeding with an axle teardown and diagnosis.