Viscous Coupler on 2002 Yukon Denali XL

We had the viscous coupler replaced at 69,800 miles on our way back from spring break this weekend the same grinding sound is coming back. It cost $2500. the first time around in August. Now the vehicle has 77K and some change. I am concerned either something was out of line at the factory making it go out the first time around or the mechanics did not get everything lined up when they replaced it only 8,000 miles ago. Your thoughts would be appreciated.

what size tires ? fore and aft?

Your truck has AWD (All Wheel Drive), doesn’t it? To prevent damage to the drive-train with AWD (which the vicious coupling is a part), all four tires have to be the SAME size. This includes the wear has to be EQUAL on all four tires. If any tire(s) is greater, or lesser, worn than the others, it (or, they) must be made equal, or all four must be replaced.

Hopefully you went to a decent shop that covers repairs labor/part 1yr/12,000 miles. AAA approved, dealers and good independent shops do this.

The truck had the original four tires replaced last month. Approximately 75k miles… they were original to factory specs. the new ones have approximately 1500 miles and were the same size as the original. I’m sorry the truck is at the shop and I cannot give you the size.

You don’t understand. EXACTLY the same size means exactly (with only a tiny bit of fudge) the same amount of wear on EVERY tire. A tire that is worn, is not exactly the same size as an unworn tire. Sure, they started life the same size; but, after a few thousand miles, they were worn to different sizes. The wear was especially different between the tires on the back axle, and those on the front axle. This resulted in a difference in circumference between the tires. This difference led to stressing the viscous coupling and its eventual failure. Continuing to run the mixed sized tires (from wear) caused the failure the second time.