I have a rubbing noise in the rear somewhere on my 1997 f150 2wd 4.2 ltr. I took it to get state inspection done on it and they said it wouldn't pass because the rear U joint was shot. I new this already because I could here the clunk when getting on and off throttle. They replaced it and the clunk went away but the cyclic rubbing noise is still there. They checked the diff. oil and had to add a quart to top off. Rubbing noise is still there. My question is, there must be some kind of leak to lose a quart of oil isn't there ? I have never seen any oil any where. Is a quart low enough to ruin any bearings ( wheel bearings, pinion shaft bearings ) etc. ? Or could this be brakes making the noise, not sure at this point any ideas appreciated. Thanks Ps. Have not had a chance to run it on jack stands or anything yet. Everything happens in the dead of winter. lol.