Ford Mustang (1999-2004) Service Manual: 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), install a new 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, install a new ring gear and pinion.

If metal has broken loose, the axle housing must be cleaned to remove particles that will cause damage. At this time, any other new parts in the axle housing must also be installed, if necessary.
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. ...
Knock
Knock, which can occur on all driving phases, has several causes including
damaged teeth or gearset.
In most cases, one of the following conditions will occur:
1. A gear tooth damaged on the drive s ...
Other materials:
Automatic transmission
WARNING: Always set the parking brake fully and make sure
the gearshift is latched in position P. Turn the ignition off and
remove the key whenever you leave your vehicle.
Your vehicle has been designed to improve fuel economy by reducing
fuel usage while coas ...
Installation
Using special tool 205-054
NOTE: This is the preferred method for installing the pinion bearing
cups. If necessary, proceed to
Using special tools 205-153, 205-054, and 205-D055 in this procedure for an
alternate method.
1. Position the special tools and th ...
Battery and Cables
Vehicles are equipped with a 12 volt maintenance-free battery that
contains a built-in hydrometer. The
hydrometer eye indication is as follows:
A green dot means the battery is OK.
A yellow dot, red dot, or when the green dot is not visible,
...
