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:
Input Shaft and Bearing
Special Tool(s)
Input Shaft Seal Replacer
308-220 (T94P-7025-AH)
Pinion Bearing Cone Remover
205-D002 (D79L-4621-A) or
Equivalent
Disassembly
1. Using the special tool and a press, remove the input bearing (7025).
2. Remove t ...
Inspection and Verification
WARNING: When servicing starter motor or carrying out other underhood
work in the
vicinity of the starter motor, be aware that the heavy gauge battery input lead
at the starter
solenoid is "electrically hot" at all times. A protective cap or boot is
provide ...
Using the boot
Installing the Boot
WARNING: Always secure the retaining clips and boot straps on
the vehicle or the boot may come loose while driving.
Note: Be sure the boot is secure on the vehicle before driving.
Improper
installation can result in loss or damage of the b ...
