Ford Fusion Quiz
Chassis

Rear Axle and Differential - Diagnosis and Testing

In this manual: Chassis
General Information — 26Chassis — 150Powertrain — 282Electrical — 271Body and Paint — 300
3steps
~18min
2/5difficulty
Done 0 of 3

Preliminary Inspection

  1. Visually inspect the housing, seals and gear flange for obvious signs of mechanical damage.
  2. If an obvious cause for the observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
  3. If the cause is not visually evident, verify the symptom and refer to the Symptom Chart: NVH.

Symptom Chart

The diagnosis in this manual assumes a certain level of skill and knowledge of Ford-approved diagnostic procedures.
REFER TO: Diagnostic Methods (100-00 General Information, Description and Operation).

Symptom Chart: NVH

Symptom Chart


Condition Possible Sources Action
Howl or whine from the axle - front or rear axle
  • Low axle lubricant level
  • CHECK the lubricant level. FILL the axle to specification.
  • Damaged axle housing
  • CHECK the axle housing for damage. INSTALL a new axle housing if necessary.
    REFER TO: Axle Assembly (205-02 Rear Axle/Differential, Removal and Installation).
  • Worn or damaged differential and gear assembly
  • CHECK the differential and carrier assembly for damage. INSTALL a new axle assembly if necessary.
    REFER TO: Axle Assembly (205-02 Rear Axle/Differential, Removal and Installation).
Transmission clunk - loud clunk when shifting from REVERSE to DRIVE.
  • Incorrect axle lubricant level
  • CHECK the lubricant level. FILL the axle to specification.
  • Excessive axle play
  • CHECK for excessive axle backlash. CHECK and, if necessary, INSTALL a new axle assembly.
    REFER TO: Axle Assembly (205-02 Rear Axle/Differential, Removal and Installation).
Transmission shudder - occurs when the vehicle begins to move forward from a stop.
  • Loose rear axle mounting
  • CHECK the bolts for looseness. TIGHTEN to specification.
    REFER TO: Axle Assembly (205-02 Rear Drive Axle/Differential, Removal and Installation).
Chatter, clunk or creak - rear axle noise when turning the vehicle
  • Incorrect or contaminated lubricant
  • TEST DRIVE the vehicle through tight circles (5 clockwise, 5 counterclockwise). DRAIN and FILL the rear axle lubricant as necessary.
  • Damaged RDU clutch - discs fused together with two-wheel drive or extended front differential to rear.
  • CHECK and, if necessary, INSTALL a new active torque coupling clutch.
    REFER TO: Four-Wheel Drive Systems (308-07 Four-Wheel Drive Systems).
  • Worn or damaged differential (differential side gears and pinions)
  • CHECK and, if necessary, INSTALL a new axle assembly.
    REFER TO: Axle Assembly (205-02 Rear Drive Axle/Differential, Removal and Installation).
Grunt - usually associated with driveline shuck experienced during acceleration from a complete stop.
  • Rear axle mounting bolts or suspension mounting bolts loose
  • CHECK the bolts for looseness. TIGHTEN to specification.
    REFER TO: Axle Assembly (205-02 Rear Drive Axle/Differential, Removal and Installation).
Whine – may occur at different speeds and driving conditions. Affects acceleration and deceleration
  • Incorrect ring and pinion contact, incorrect bearing preload, or gear damage
  • CHECK and, if necessary, INSTALL a new axle assembly.
    REFER TO: Axle Assembly (205-02 Rear Drive Axle/Differential, Removal and Installation).
Clunk – heard during coasting or braking. Also described as knocking
  • Incorrect ring and pinion contact or damaged teeth on the ring and pinion drive side
  • CHECK and, if necessary, INSTALL a new axle assembly.
    REFER TO: Axle Assembly (205-02 Rear Drive Axle/Differential, Removal and Installation).
Knock – noise occurs at different speeds. Does not depend on acceleration or deceleration.
  • Drive side ring gear and pinion tooth damage.
  • CHECK and, if necessary, INSTALL a new axle assembly.
    REFER TO: Axle Assembly (205-02 Rear Drive Axle/Differential, Removal and Installation).
Scraping noise – a continuous low-frequency noise that starts at low speed.
  • Worn or damaged pinion bearings.
  • CHECK and, if necessary, INSTALL a new axle assembly.
    REFER TO: Axle Assembly (205-02 Rear Drive Axle/Differential, Removal and Installation).
Driveline shudder - occurs during low speed acceleration or stopping.
  • Rear drive axle assembly is incorrectly positioned.
  • CHECK the axle mounts and rear suspension for damage or wear. Repair as necessary.
    REFER TO: Axle Assembly (205-02 Rear Axle/Differential, Removal and Installation).
  • Rear axle bolts loose.
  • CHECK the rear axle for loose bolts. TIGHTEN the bolts as necessary.
    REFER TO: Axle Assembly (205-02 Rear Axle/Differential, Removal and Installation).
  • Driveline angles do not meet specification
  • CHECK the driveline angles for correctness.

Leak Analysis

Clean the leak area sufficiently to determine the exact source.

A clogged RDU (rear drive unit) vent may cause excessive pinion seal lip wear due to increased internal pressure.

Make sure the RDU lubricant level is 3-5 mm (1/8-3/16 in) below the bottom of the fill hole.

Axle Vent

A clogged vent will cause excessive wear of the seal lip due to internal pressure buildup. If leakage occurs, check the vent. If the vent cannot be cleaned, install a new vent.

Pinion Seal

The pinion seal is not serviceable at this time.

Pinion Nut

The pinion nut is not serviceable at this time.

Differential Seals

NOTICE: When installing the axle shafts, do not allow the splines to contact the seals during installation, otherwise seal damage may occur.

Axle shaft housing bearing support seals are subject to the same types of damage as the pinion seal if incorrectly installed. The seal bore must be clean and the edge handled carefully to avoid cuts and tears. The seal journal surface must be free of nicks, grooves and rough texture.

For differential seal information, refer to: Rear Axle Shaft Seal (205-02 Rear Drive Axle/Differential, Removal and Installation).

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