Ok. I'm used to all the usual noises and rattles from my 2013 M3W. There was a new one today that I'm having trouble identifying. At low RPM and speed there's an occasional slamming sound that seems to come from either the rear of transmission, drive shaft, or BB. It sounds and feels like a single hammer hit to the frame just under the seat. I can't seem to figure out what sequence causes it, but it has happened a few times. It's not the Centra compensator drive, nor is it the clutch.
Thoughts?
