Vibration From Approximately 56 To 62 MPH (90 To 100 kph) - keywords axle boom differential RDM

This PIwas superseded to update Recommendation/Instructions. Please discard PIP4172.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some customers may comment on a vibration concern from approximately 56 to 62 MPH (90 to 100 kph). The customer may also comment that the vibration goes away at higher speeds, and then returns at approximately 78 MPH (130 kph). In some cases, this vibration may be strong enough to cause a resonant body boom; a low-frequency, high-pressure resonance, similar to driving with the rear windows part way down.

Verify the concern on a vehicle road test. Diagnose the vehicle using the Vibration Diagnosis and Correction information in SI (Doc ID #1578894). Use the Electronic Vibration Analyzer (J 38792 A) to verify that the vibration is a 1st order (propshaft speed) disturbance. To Isolate the concern re-index the propshaft by 180 degrees and road test the vehicle to determine the effect on the concern. If there is no change in the vibration, it may be caused by a different driveline component.

The vibration may be reduced or eliminated by re-indexing the propshaft. If the vibration is not eliminated by re-indexing the prop shaft and is still showing a 1st order vibration or boom that peaks in the speed ranges above, it may be caused by an out-of-balance condition in the Differential Carrier Assembly. It would be necessary to replace the (RDM) Rear Drive Module (including the clutch drum assembly).

If the concern is eliminated by re-indexing the prop shaft no further repairs are required.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.