Inspect for the proper gear oil levels prior to performing system diagnosis. Refer to Lubricant Change .

Loose propeller shaft mounting bolts

Tighten the bolts as required. Refer to Propeller Shaft Replacement in Propeller Shaft.

Worn, loose, or missing differential mounts

Repair or replace the differential mounts as required.

Loose torque tube bracket or a damaged bracket bushing

Tighten the bracket bolts or replace the bracket as required.

Incorrect type fluid

Installation of the incorrect type gear oil may create a "moan" type noise within 7 770-25 900 km (3-10,000 miles). Fluid that is "black" in color is to be considered normal and is darkened by the carbon material in the clutch plates.

Replace the rear differential assembly as required.

Fluid replacement will not correct a "moan" condition caused by the use of incorrect oil. Refer to Differential Replacement .