I need some help guys. I have been chasing this dogs tail now for a few weeks and 300 plus and no better off. I have a 2004 F-150 4x4 with manual engagement. When I am in 2 wheel high the truck has started to make a sound like a bad bearing, or dragging aluminum on the ground behind me. No problem with transmission I have changed hub bearing on drivers sides along with cv joint and replaced both front diff and transfercase fluid, and also taken front diff cover off with no apparent problem. It only make this noise in 2 wheel high, not in 4 wheel high or low. Any Ideas would be helpful. Thanks..........

 

Were you able to check all the u-joints on the drive shafts? Sounds like one of them is going dry.

 

I would agree with the u joints idea. Got a 2001 4 wheel drive and the front u joint at the tcase snapped and made a pretty similar noise to the one you described. Just hope that your u joints don't give you any issues like mine did. Had to put on a new driveshaft in the end.