Ey they I have loud noises coming from underneath. It only happens in the 5 to 15 MPH range after that it subsides until I get back in that area. I had a friend drive and I thought it was coming from the center of the truck. Looked and found a seal blown on the transfer case. Pulled the back end off and the bearings seem to be fine no wear. Also drained it and it was darker than normal. Checked all wheel bearings and they are good. Any ideas?