blackrat

My car has 70k on it, and to my knowledge has had no rear end service. I've been holding out because I am going to be installing a girdle,solid pinion, and lower gears next month. Anyway, I rarely drag my car but do shift hard and drive pretty hard, but I haven't had any problems with my 10 bolt till now.

Whenever I go to back up I hear and feel a slight clunk coming from the rear. All forward motion is fine though, and I don't hear any whining or any noise whatsoever even on hard shifts.

I'm not going to have any time to get it up on jacks until the weekend but what things should I look for? I have been in and out of the area recently with my clutch install (TA, ypipe, etc) and soon after a rear tranny seal replacement (same, TA, ypipe, driveshaft) but I tightened everything down pretty good. One thing that could be going on is my tranny mount has a tear/crack in it, but it's not that bad. I just haven't gotten around to picking up an upgraded one yet. Could that be leading to the sound? Am I in any dager of the rear blowing? If that's the case I will stop driving around until everything else is ruled out.