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

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.

Access the final drive internal gear and mark the current orientation to the case. Remove and rotate the internal gear 180 degrees from current marked location and reinstall internal gear to transmission case. Evaluate noise as noted above, noise level should be reduced. If not, contact TAC for next step. Replacement of the final drive, sun gear and internal gear may not result in reduction of the noise level

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.