Update from an earlier post, I have a 1999 F-150 that I had the 8.8 rear differential rebuilt about 3500 miles ago. Recently I have been hearing a growling noise from the rear unit so I took it back to the shop that did the work to have it checked out. My mechanic called and said the noise was clutch chatter and to contact Eaton about a possible warranty replacement (I bought the part myself and brought it to him). After contacting Eaton they are saying to replace the oil that was put in it at installation (motorcraft) with Mobil 1. If that doesnt fix the problem then the carrier would have to come out, be sent back to the place of purchase then go to Eaton for inspection, takes 2-4 weeks. Would the oil have an impact on the performance and has anyone had any dealings with Eaton parts warranty?

 

pretend the differential had a FACTORY friction clutch, then it normally need FRICTION MODIFIER or it will chirp and chatter in cornering........ Depending on what type material is used in the EATON clutch, it may have a different coefficient of friction and need a specific oil... That may work.

Think of the FORD transmissions... some need MERCON V, some need MERCON LV, etc.. the difference is what are the PLATES made of and what friction they have and how much slip is acceptable. Plates can be brass, compressed paper, or something like brake material... all have a different coefficient of friction and slip.

 

Try the fluid thing first. My Eaton Truetracs require non-synthetic oil.