It could be something as minor as a low fluid condition or even low voltage from the battery causing the issue. It could also be a failure in the transmission.
The safest bet is to take it immediately to a reputable facility to have it properly checked out. The longer you drive it in this condition, the more likely you are to cause serious issues. If oine shop says you need a new torque converter or a rebuild, make certain to get a second opinion before having it completed, maybe even try a few BMW specialists.
Thursday, March 3rd, 2011 AT 11:11 AM