'85 GSL with 53,000 miles on it, I've only owned it for a couple of months now. Just the other day, I noticed that it started "clunking" when I would start off or shift from 1st to 2nd, as well as if I was decelerating and let the car "buck" a little (let the rpm's drop low and not downshift). Jacked the rear of the car up tonight thinking I would diagnose the u-joints quick and was surprised to find that they are definitely not the problem. U-joints are snug as can be. Gear oil was changed less than 300 miles ago and I did check the fluid level tonight, it's right up where it should be. The problem is coming from somewhere in the rearend. Videos are below of the noise with the car jacked up... seems like it may be more pronounced from the left wheel, but not entirely sure... Any help is appreciated!!

Right side:
http://www.youtube.com/watch?v=iRwdRBGvhwo


Left side:
http://www.youtube.com/watch?v=rO_U9dqUagg

 

It's likely excessive backlash between the ring and pinion, the solution is a rebuild/refresh to clean up and snug up everything.

 

that is just ring and pinion back lash, does the rear end make noise when driving like a howl or bearing noise? if not just keep driving it. My lsd has a lot of slop also, just dont let it buck on decel and be nice to it and it will last a long time.

 

Mine does the same thing! I have noticed the sound if I coast and just shift between the gears while holding the clutch in. I only notice it when I shift up. I also drive my car like I am trying to break something and it's held up fine. I clutch kick it a lot as well and nothing seems to be getting worse.

 

So the clunking is nothing to be too concerned with? I can keep driving it without worrying about the rearend coming apart on me?