Hello,

When I startup my '89 244 in the morning (or whenever the engine has had a chance to cool down completely), there's a noticeable grinding/vibration. It seems like it's coming from the rear center, underneath the car (around the exhaust or differential).

This noise happens immediately on startup (in Park), and continues when I put it in reverse (backing out of a parking spot, etc), but goes away when I put it in drive and take off.

The noise sounds like it's related to the exhaust somehow, and I recently replaced the exhaust between the mufflers, but it really doesn't look like the exhaust is making contact anywhere on the car. All the ring clamps are tight, and it doesn't really move when I pull on it in various spots.

If it helps, I can probably post an MP3 of the noise - let me know and I'll break out my microphone later.

Here are a few theories that kind of make sense to me - please let me know which sounds most promising, or if you have other ideas:
1. muffler hangers - these are pretty old and looking rough.
2. transmission mount - I replaced the engine mounts a while back, but haven't gotten around to the trans mount yet - could this be the culprit? (and advice on where/how to best support the trans while I replace the mount would be appreciated, too)
3. transmission linkage - I had to replace one of the clear bushings a while back when my shifter (auto) started wobbling around. It seems to shift ok, but I'm wondering if I should try to fine-tune the linkage adjustments due to the new bushing?
4. Something Else Entirely - suspension? rear axle? I'm pretty new to wrenching, so I don't really know where to start with these.

Any advice would be greatly appreciated!