Some Chevy LCF (Chevy Low Cab Forward) customers may notice that their medium-duty truck makes a clicking or chattering noise around the rear of the vehicle while making tight turns. Now, a possible cause for this issue has been identified, as has a fix.
According to a recent report from GM TechLink, this issue may be present on 2016 through 2023 Chevy LCF 3500 / 4500 models, 2017 through 2023 Chevy LCF 4500HD / 4500XD and LCF 5500HD / 5500XD models, and 2019 through 2020 Chevy LCF 6500XD models. Affected models are equipped with either the naturally aspirated 6.0L V8 L96 gasoline engine, or the 5.2L I4 4HK1 turbodiesel engine, as well as a limited-slip rear axle, or limited slip differential (RPO code G86).
According to GM TechLink, the clicking or chattering noise may be coming from the rear axle during turns as the result of incorrect axle fluid in the differential. This fluid may have been added during regular scheduled maintenance or during a previous repair. Alternatively, the sound may be the result of degraded axle fluid, which should be replaced during regular maintenance.
To address this issue, GM TechLink recommends that a GM technician check that the affected vehicle is in fact equipped with a limited-slip rear axle by checking the vehicle build in IVH for code G86, or by checking for the following LSD stamp codes on the axle:
Any incorrect or degraded rear axle fluid (or differential gear oil) should be replaced with the correct oil, specifically SAE80W-90 GL-5, SAE90 GL-5. Additionally, limited-slip differential lubricant additive should be added as well. GM technicals should add fluid within 0 to 10 mm of the bottom of the fill hole.
Once the appropriate fluid has been added, it’s recommended that the technician takes the Chevy LCF for a test drive that covers at least 10 miles, during which the driver should make roughly ten left and right turns to ensure that the limited-slip rear axle is activated and the clicking noise is no longer present.