I have had a re-ocurring problem with my 2004 QS 1500HD and the dealership cannot figure it out. The rear end will make a ugly grinding noise while in reverse and gets louder while turning. I have had it to the dealer several times they alwys say "unable to reproduce customer complaint" The problems is it happens randomly. Has anybody had this problem and can they put a name to it?

Sounds like it could be the rear end fluid. Look around on here, seems the G86 LSD is very sensitive to the type and amount of fluid additive needed. The noise will also develop over time from what I understand, may be he additive breaking down. I would go to the dealer and get some Quadrasteer axle oil and change it out. Drive it around for a couple hundred miles and see if it gets better.

Bob

I had the same sound in my Chevy 2500. It started after the dealer put the wrong Diff fluid in the rear end. You have to use the exact fluid that it calls for in their service manuals. If you have not changed the Diff fluid, have them do it but make sure they put the correct fluid in that GM or Chevy calls out. After putting the correct fluid in my 2500 the noise went away in about 2 weeks after the fluid got worked in.

If you have any questions you can get a hold of me at Matt [at] deleonthompson.com

Hope this helps.

Don't assume the dealer would know what to put in to the differential. Most dealers don't aware that the QS differentials are limited slip, and they need special differential fluid, not the one they use for the lockers. Check truck's owner manual for the right differental fluid part number. If you don't have the manual, search this site for the differential, fluid part number.

I purchased Video on ebay about how to service our trucks (created back in Jan of 2002). They had live questions and answers asked. A tech actually called in and said very few techs will pay attention to the correct part # for the QS gear lube. Most techs will use the standard gear lube which will result in a complete QS replacement. The nerve of SOME people that will mess with us.