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:
Installation
1. Install a new upper intake manifold gasket.
2. NOTE: Refer to the location note made during removal and make sure
the bolts are installed in
the correct locations.
Install the upper intake manifold. Tighten the bolts in two stages in the
sequence shown ...
Idle Air Control (IAC) Valve - Cobra
Removal and Installation
1. Disconnect the idle air control (IAC) valve electrical connector.
2. Remove the bolts, the IAC valve and the gasket.
3. NOTE: Install a new gasket if necessary.
To install, reverse the removal procedure. ...
Brake Shift Interlock Actuator
Removal
1. Remove the shifter top control panel.
2. Disconnect the electrical connectors.
3. Remove the shifter bezel.
4. Remove the bulb from the bezel.
5. Disconnect the electrical connector.
6. CAUTION: Extra force may be needed to lift up on th ...
