An audible clicking sound or chattering noise from the rear of the vehicle while making tight turns may be heard on some 2016-2023 LCF 3500/4500; 2017-2023 LCF 4500HD/4500XD, LCF 5500HD/5500XD; and 2019-2020 LCF 6500XD models equipped with the 6.0L V8 gasoline engine (RPO L96) or 5.2L 4-cylinder diesel engine (RPO 4HK1). Affected vehicles also are equipped with a limited-slip rear axle, or limited-slip differential (LSD), (RPO G86).
The sound from the rear axle during turns may be caused by the use of the incorrect axle fluid in the differential, which may have been added during scheduled maintenance or a previous repair. If regular maintenance is not performed, the degraded axle fluid also may lead to rear axle noise.
Verify the vehicle is equipped with a limited-slip rear axle by checking the vehicle build in IVH for option code G86 or look for the following LSD stamp codes on the axle: B7, D0, D8, D9, H0, or H9. (Fig. 1)
Fig. 1
The incorrect or degraded rear axle fluid (differential gear oil) should be replaced with commercially available gear oil (SAE80W-90 GL-5, SAE90 GL-5). Also add limited-slip differential lubricant additive.
Always check the Recommended Fluids and Lubricants in the appropriate Service Information for the proper fluid for maintenance and repairs. Fluid should be added to the rear axle within 0-10 mm (0-0.4 inches) of the bottom of the fill hole. (Fig. 2)
Fig. 2
After adding fluid, road test the vehicle for at least 10 miles and make approximately ten tight left and right turns, such as going around a corner, to ensure the limited-slip rear axle is activated. An audible clicking or chattering noise should no longer be heard coming from the rear of the vehicle during the tight turns.
Refer to Bulletin #22-NA-223 for more information, including part numbers.
– Thanks to Richard Renshaw
