Ford Mustang Service Manual: Gear Howl and Whine

Driveline System

Special Tool(s)

Clamp Plate Clamp Plate 205-320 (T92L-4851-C)
Clutch Housing Alignment Clutch Housing Alignment Adapter 308-021 (T75L-4201-A)
Companion Flange Holding Companion Flange Holding Tool 205-126 (T78P-4851-A)
Companion Flange Runout Companion Flange Runout Gauge 205-319 (T92L-4851-B)
Dial Indicator with Bracketry Dial Indicator with Bracketry 100-002 (TOOL-4201-C) or equivalent
Dial Indicator/Magnetic Base Dial Indicator/Magnetic Base 100-D002 (D78P-4201-B) or equivalent
Vibration Analyzer Vibration Analyzer 100-F027 (014-00344)
Traction-Lok Torque Tool Traction-Lok Torque Tool 205-022 (T66L-4204-A)

Inspection and Verification

Certain axle noise or vibration symptoms are also common to the engine, transmission, wheel bearings, tires, and other parts of the vehicle. For this reason, be sure that the cause of the trouble is in the axle before disassembling, adjusting or repairing the axle. Certain driveshaft vibration symptoms are common to the front engine accessory drive (FEAD), the engine, transmission or tires. Be sure the cause of the concern is the driveshaft before repairing or installing a new driveshaft. Certain symptoms may be caused by Traction-Lok differentials (4026). Check the vehicle certification label and axle identification tag to determine the type of differential.

Noise Acceptability

NOTE: A gear-driven unit will produce a certain amount of noise. Some noise is acceptable and audible at certain speeds or under various driving conditions such as a newly paved blacktop road.

Slight noise is not detrimental to the operation of the axle and is considered normal.

With the Traction-Lok differential axle, slight chatter noise on slow turns after extended highway driving is considered acceptable and has no detrimental effect on the locking axle function.

Universal Joint (U-Joint) Inspection

Place the vehicle on a frame hoist and rotate the driveshaft (4602) by hand. Check for rough operation or seized U-joints. Install a new U-joint if it shows signs of seizure, excessive wear, or incorrect seating.

Analysis of Leakage

Clean up the leaking area enough to identify the exact source. An axle leak can be caused by the following.

  • Axle lubricant level is too high.
  • Worn or damaged axle shaft seals or differential seals.
  • Differential housing is cracked.
  • Flange yoke seat is worn or damaged.
  • Pinion flange is scored or damaged.
  • Axle cover is not sealed.
  • Vent is plugged.

Repair the axle as necessary. Make sure the axle lubricant is at the correct level. Refer to Specifications in this section.

Axle Vent

NOTE: If a plugged vent cannot be cleared, install a new one.

A plugged vent will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the vent. Make sure the vent hose is not kinked. Remove the hose from the vent nipple and clear the hose of any foreign material. While the hose is removed, pass a length of mechanics wire in and out of the vent to clean it. Connect the hose when done.

Flange Yoke Seal

Leaks at the axle drive pinion seal originate for the following reasons:

  • Seal was not correctly installed.
  • Poor quality seal journal surface.

Any damage to the seal bore (dings, dents, gouges, or other imperfections) will distort the seal casing and allow leakage past the outer edge of the axle drive pinion seal.

The axle drive pinion seal can be torn, cut, or gouged if it is not installed carefully. The spring that holds the axle drive pinion seal against the pinion flange may be knocked out and allow leakage past the lip.

The rubber lips can occasionally become hard (like plastic) with cracks at the oil lip contact point. The contact point on the pinion flange may blacken, indicating excessive heat. Marks, nicks, gouges, or rough surface texture on the seal journal of the pinion flange will also cause leaks.

When a seal leak occurs, install a new seal and check the vent and the vent hose to make sure they are clean and free of foreign material.

Axle Shaft Seals

Axle shaft oil seals are susceptible to the same kinds of damage as axle drive pinion seals if incorrectly installed. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. The axle shaft journal surface must be free of nicks, gouges, and rough surface texture.

Analysis of Vibration

WARNING: A vehicle equipped with a Traction-Lok differential will always have both wheels driving. If only one wheel is raised off the floor and the rear axle is driven by the engine, the wheel on the floor could drive the vehicle off the stand or jack. Be sure both rear wheels are off the floor.

Few vibration conditions are caused by the rear axle. On a vibration concern, follow the diagnosis procedure in Section unless there is a good reason to suspect the axle.


WARNING: Do not balance the wheels and tires while they are mounted on the vehicle.

Possible tire disintegration/differential failure could result, causing personal injury/extensive component damage. Use an off-vehicle wheel and tire balancer only.

Most vibration in the rear end is caused by tires or driveline angle.

Vibration is a concern with modern, high-mileage tires if they are not "true" both radially and laterally.

They are more susceptible to vibration around the limits of radial and lateral runout of the tire and wheel assembly. They also require more accurate balancing. Wheel and tire runout checks, truing and balancing are normally done before axle inspection.

Driveline Angle

Driveline angularity is the angular relationship between the engine crankshaft (6303), the driveshaft, and the rear axle pinion. Factors determining driveline angularity include ride height, rear spring, and engine mounts.

Wheel Hub or Axle Flange Face Runout
Wheel Hub or Axle Flange Bolt Circle Runout NOTE: The brake discs must be removed to carry out all runout measurements. 1. Position the special tool perpendicular to the wheel hub or axle flange bol ...

Bearing Whine
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 d ...

Other materials:

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Axle Housing
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