Rear Axle Moan During Turns

Some 2020-2022 CT4 and CT5 models equipped with the limited-slip differential (RPO G80) may have a moan sound during left or right turns. The condition may be caused by a stick/slip effect of the posi-traction clutch plates in the Rear Differential Module (RDM) of the rear axle.

If the sound is present, flush the fluid from the RDM and refill it. (Fig. 4) Refer to Rear Axle Lubricant Replacement in the appropriate Service Information. When filling the rear axle, fluid should be even with the bottom of the fill plug hole or no lower than 2mm (0.08 inches) below the opening.


Fig. 4


After flushing and refilling the RDM, if the sound is still heard under the same conditions, flush and refill the RDM one more time. If the sound is present after two refills of the RDM, the RDM (Fig. 5) should be replaced. Refer to Differential Carrier Assembly Replacement in the appropriate Service Information.


Fig. 5


For more information, including part numbers, refer to Bulletin #22-NA-091.

– Thanks to Robert Cross


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