1990 Suburban. It has sat for 7 years before I got it. Lady said the rear end was shot. When i drove it the u joints sounded bad. Changed them. They where bad. It still sounds like someone is hitting the drive line with a hammer when driving slow and the tranny shifts. i pulled the differential it looks OK. With the carrier out & tranny in park, I can rotate the drivline at least 1/4 turn. Could it be the chain in the transfer case? 1500, 4x4, 10 bolt, new prosses.