I have the same problem. read all your posts and figured id change the driveshaft u joints. There was nothing wrong with the old u joints but i changed them anyway. Problem solved! So i thought.... For the first couple of weeks it was like brand new. Tight as can be and i was happy and then it slowly returned. not sure what to do now. its gotta be in that area being that it tightened up. gonna re-grease and see what happens.