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:
Diagnosis By Symptom
Special Tool(s)
Transmission Fluid Pressure
Gauge
307-004 (T57L-77820-A)
Air Test Plate, Transmission
307-246 (T92P-7006-A)
Breakout Box, EEC-V Control
System
418-049 (T94L-50-EEC-V) or
equivalent
MLP- ...
Rear-view camera system
WARNING: The rear view camera system is a reverse aid
supplement device that still requires the driver to use it in
conjunction with the interior and exterior mirrors for maximum
coverage.
WARNING: Objects that are close to either corner of the
bumper or under ...
Engine coolant check
Checking the Engine Coolant
The concentration and level of engine coolant should be checked at the
intervals listed in Scheduled Maintenance Information.
Note: Make sure that the level is at the FULL COLD level or within the
COLD FILL RANGE in the coolant res ...
