Noise Conditions

- Gear noise is typically a howling or whining of the ring gear and pinion due to an improper gear pattern, gear damage, or improper 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 occur on acceleration or deceleration. The teardown will disclose what service is required.
- Chatter on corners occurs when the whole rear end vibrates only when the vehicle is moving. The vibration is plainly felt as well as heard. In conventional axles, extra differential thrust washers cause a condition of partial lockup that creates this chatter. Chatter noise on Traction-Lok (R) axles can usually be traced to erratic movement between adjacent clutch components and can sometimes be corrected with a lubricant change and the addition of Additive Friction Modifier C8AZ-19B546-A or equivalent meeting Ford specification EST-M2C118-A.
- Click at engagement is a condition when the axle produces a slight noise, distinct from a clunk, that happens in REVERSE or DRIVE engagement. Check for the presence of a pinion oil slinger.
- Axle shaft noise is similar to gear noise and pinion bearing whine. However, rear wheel shaft bearing noise will normally distinguish itself from gear noise by occurring in all driving modes (drive, coast and float) and will persist with transmission in NEUTRAL while vehicle is moving at a certain speed. If vehicle displays this noise condition upon ride evaluation, remove suspect axle shafts, replace wheel seals and install a new set of axle shafts. Re-evaluate vehicle for noise before removing any internal rear axle components.
- Boom occurs when ring gear teeth have a backlash variation of more than 0.10 mm (0.004 inch).

Any damage to a gear tooth on the coast side can cause a noise identical to chuckle. Even a very small tooth nick or ridge on the edge of a tooth is enough to cause the noise.

This condition can be corrected and the noise eliminated by cleaning up the gear tooth nick or ridge with a small grinding wheel. If the cleaned up or damaged area is larger than 3.2 mm (118 inch), replace the gearset.

If either gear is scored or damaged badly, the gearset must be replaced. Also, if metal has broken loose, the carrier and housing must be cleaned to remove particles that could cause damage later. Any other damaged parts in the axle must be replaced.












To check the gearset, 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.

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

The noises 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.

Knock, which can occur on all driving phases, has several causes. In most cases, one of the following conditions has occurred:
- 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.
- Knock is also characteristic of excessive end play in the axle shafts. The knock will be less frequent because the axle shaft speed is slower than the driveshaft.

Be sure to measure the end play with Dial Indicator TOOL-4201-C or equivalent, not by feel.

On the integral axle, end play is allowable up to 0.762 mm (0.030 inch) but can be reduced to 0.127 mm (0.005 inch). It is controlled by the C-washer that holds the shaft in the pocket of the side gear.