Need help pinpointing vibration on a 2000 323i auto steptronic

I have a 2000 323i steptronic transmission, am33. 109689miles
I have a intermittent vibration that feels like it's coming from the rear. I thought it was coming from the right rear tire but my girlfriend swears it's coming from the left rear tire so that makes me think it's starting at the diff. The best way I can describe it is it feels like I'm hitting a rumble strip for a second and the car pulls back. You can feel the resistance in the rear end and the tach drops in rpms. I made a video of the tach when it happens, this is a less severe occurrence then normal but I frigured a video would help more than me trying to explain it. Any help is appreciated. Thanks in advance.

I should also mention that there are no codes and the vibration occurs in all tranny modes, d, s d, and m. I thought it was the transmission for awhile but it doesn't do it under acceleration. It only seems to do it when i'm driving at a steady rpm.

Thanks for all the "help" guys. Found the problem. Think I can press a new one in with a c clamp, alot of patience, and a breaker bar?




hope this helps someone else.

I hate to be the barer of bad news but I replaced my rear diff mount bushing and things have only gotten worse. The intermittent vibration is still there only worse but not only that I have a constant vibration all the time now. My new theory is it's a drive axle. left side.

Look at your flex disc first. I have never seen a bmw axle cause a vibration that you are describing. If flex disc appears ok, then driveshaft could be culprit of vibration....

update: changed out the rtabs to uuc rtabs. also changed the rotors thinking that was it but no luck. $130 dollars and a chemical burn later nothing.