A few years back my rear end was chattering while turning so i changed the fluid using motorcraft fluid and additive. Know I noticed that the cover is leaking so I wanted to change the fluid but started thinking It wouldn't make sense to change the fluid when I will eventually need to change the clutches which would require another fluid change. So Has anyone changed the clutch packs themselves? and how difficult is it? Also it seems like the truck has a whine on the interstate, i'm not sure if this is from my tires (General Grabber AT2) or the rear end bearings. By the way the truck is a 2002 F150 Fx4 with a 9.75 inch ring and 3.55LS with 159,000 miles on it