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.