The problem is solved. You guys need to know this.
I went to one of the three Jeep dealerships I get my Jeeps serviced at and talked to the Service Manager, whom I know. He told me "You need to talk to George". George is a senior mechanic and that is not his real name, and you'll soon know why. George wanted to retire 3 years ago and now he's cranky because they keep begging him to keep working at age 68. He tells the truth even when it's against DCX policy.
The story: The 1999-2001 differential fluid specification for Trac-Loc axles was changed via TSB in late 2001 from 75W140 GL-5 Synthetic (Mopar® P/N 04874469) to 80W-90 GL-5 (Mopar® P/N 04874468). If you use the 75W140 specified in your owner's manual, your Trac-Loc clutch disks will be well and truly worn out by the next scheduled fluid change. While wearing out they will make a groaning noise which is what mine were doing.
This fact has NOT been communicated to the customers, and the owner-manual-specified 75W140 fluid is correct for 2002+ axles, after a mechanical change to the Trac-Loc. However there are literally thousands of 1999-2001 Trak-Loc's out there with worn-out clutches due to the incorrect fluid specification. DCX has put in place a "customer goodwill" policy to replace these diffs with new ones (about a $750 repair) if it is documented that A) the damage occurred due to the incorrect fluid and B) the tire size has not been changed, or any other change which invalidates the powertrain warranty. However, you need to know your Trac-Loc is not working to know you have a problem, and 99% of the customers do not have any idea.
I found this story slightly mind-boggling, but it appears to be true. Today after approximately 40 miles with the 80W90 lube in both diffs (and another two bottles of friction modifier) the groaning noises stopped. I have the dealership documentation if any subsequent diff failures occur, but "George" assures me the problem was resolved in the first 250 miles with no damage.
Gary
