I have been getting a lot of howling coming from my rear differential for some time now. The shop told me everything looked with the rear diff and that it was just normal. I have a 2004 Super Crew with a LS and was wondering if adding some friction modifier would help. I have read that this has been a problem with some Fords. If so what kind and would I need to completely drain the diff. to add it?

 

How many miles on the truck and has the diff fluid ever been changed? Stock gears?

 

about 69,000 and fluid was changed about 1 year ago, and yes stock gears.

 

Friction modifier was supposed to have been added if you have a LSD when the fluid was changed, was it? If not, I would consider changing the fluids again and adding the modifier. At least add it if nothing else.