Heh, I know exactly what you're talking about. Those of you trying to picture this, he's referring to the inner bolt that mounts the lower control arm to the subframe. Yes, unfortunately the diff has to be unbolted; it's a bad design on BMW's part. The towing company should pay for the damages tho. For future reference, this is a common occurence. I don't know about other models, but the 3 series should never be hooked, they have to be dollied from under the wheels or flatbedded, and the towing company should have known that.