Help diagnose driveshaft slap on 332ti!

[alexw]

Hello there. I've been a long time member, but just recently purchased a 1997 318ti with a S52 swap. The swap was "professionally" done in 2001, I have receipts that show an insane bill for the conversion. I just recently purchased the vehicle.

The original 318ti transmission and driveshaft were reused during this swap.

I'm having what I can best describe as driveshaft slap under hard acceleration. I am able to lightly operate the vehicle without causing the shake or slap, however under normal acceleration from a stop, it is present. Under hard acceleration its extremely violent. The previous owner thought the issue was the rear subframe and trailing arm bushings. He had this to say about it:

There seem to be multiple issues that can create similar symptoms. It was kind of the same when the flex disc (guibo) in the drive shaft was shot. That got progressively worse until I changed it. Then it was fine. Some time after that, the right rear shock tower / mount broke.(different, very obvious symptom) I fixed that with a reinforcement kit and installed those on both sides. I suspect the shock mount breaking may have caused a weakness in the rear bushings. Then when I started to get the current symptom, I inspected the rear dif mount and it was separating, so I replaced it. That didn’t fix it, next I replaced the center support bearing. That didn’t fix it. That’s when I replaced the drive shaft because the universal joint was not operating smoothly. It hasn’t really progressed.

So, because everything else back there has been changed, I think it’s the rear trailing arm / sub frame bushings. That would have been my next course of action. From what I could see, all the metal on the rear sub-frame and trailing arms looks pretty solid.

I had several car savvy (and bmw nuts) ride and drive my vehicle. All signs pointed to a worn center support bearing. I went ahead and ordered OEM center support bearing and transmission mounts. Last night, a few friends got together and worked on my car. We found a completely shot center support bearing. The bearing was still securely on the driveshaft but the rubber around that was completely worn off, so basically the driveshaft was free floating in the center support bearing.

We felt fairly confident that the new center support bearing would fix the issue, thinking perhaps the previous owner lied or installed it incorrectly. Unfortunately, this did NOT fix the driveshaft slap.

Some things to note:
- Driveshaft IS new. Still has stickers on it, it looks very fresh. I've sent an email to the previous owner asking for more details on it, i.e. install date, brand, etc.
- Flexdisk or "Guibo" looks fine
- I put the vehicle on jack stands and put it in gear and accelerated, I did not feel the shake. That being said, I didn't exactly beat on it while I was up there. So take that for what its worth.
- While rotating the driveshaft, I noted only the passenger rear wheel was turning. I have receipts for a Limited Slip but have no idea what one is on there. Is that normal?
- Fairly certain this isn't a rear subframe bushing issue. Under inspection they don't look that bad.
- Engine Mounts look fine.

Any advice would be greatly appreciated.

*** If this would be better located in a different section, I apologize. I'm not sure if this may be an issue due to the swap, or choice of transmission. ***