Re-Manufactured abs pump question

[truitta]

2008 BMW 328i.
Sent my ABS module out for re-manufacture. It was removed and reinstalled by a good indie garage. After reinstall brakes were bled per instructions. On my way home after about 20 minutes of driving I started getting vibrations as I would accelerate away from traffic lights. Normal acceleration. The vibration was such that I initially thought I was going from smooth pavement to slightly rough. The car would vibrate in various speed ranges approx. 30/45/57 mph. Called my garage and they said it had to be something other than the abs repair as they have done many abs installations. They advised me to drive the car for several days and wait for a new problem light, then bring it in. I drove the car daily for 5 days. Vibration only starts after about 20 minutes of driving. No new lights. Took the car in today and they spent 3 hours trying to find the problem. Couldn't find anything. I asked for a re-bleed and they did that. Still vibrated.

The garage mechanic thinks the problem is with the transmission and just happened to occur right after installation of the abs unit. They don't work on transmissions and advised me to take the car to a transmission shop. The vibrations do not occur when the Steptronic is placed in manual mode.

Before I start an expensive exploration of the trans, has anyone else experienced or have knowledge of a problem like this