I bought a 2002 dodge ram 2500 van last week. Within days, the rear end starting making a grinding noise when turning at low speeds. Pep boys said it needed two rear u-joints, which I had done but did not fix the problem. Truck only has 86k on it. I suspect it needs a rear differential. Any ideas on cost? Are these differentials a common problem? Thanks. Tim

 

The Diffs are commonly ignored until they make noise.

Limited slip differential diagnosis is different than open differential.

With an open diff, and both wheels lifted off the ground, spinning one wheel will spin the opposite wheel, in the opposite direction

 

You can try a drain and refill to see if the noise goes away. If it doesn't then the previous owner probably threw something in the differential to make it run quiet long enough to dump in on someone.

 

Since your Ram Van is made after 1998, Chrysler has a TSB stating that a synthetic 75W90 is required for the rear. If you have noise, drain the rear by removing the plate, clean it out super good, and get a nice feltpro gasket to remount the plate. Then refill with the Redline synthetic 75W90 with the friction modifier. Their formula meets/exceeds the Chrysler requirements.