Low Speed (15-30 MPH) Final Drive Whine Noise 2007-08 Cadillac DTS 4T80E MH1 Transmission - keywords drive final gear howl internal low moan noise slow speed whine

This PI was superseded to update the repair procedure. Please discard PIP4231.

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

Several TAC cases with reported final drive whine noise. Noise seems to be present in the 15-30 mph range. Noise should be evaluated at approximately 19 mph with radio off; HVAC should be on fan speed 3. Compare complaint vehicle to like vehicle. If complaint vehicle is louder than like vehicle and noise can be heard above fan speed 3 with radio off, proceed with the following repair.

Replace internal gear (120), sun gear (121) and final drive carrier (100)".

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.