I recently aquired a 1986 740 Turbo Wagon(M46 Trans) with 180,000 miles on it, but it will not move in reverse. It shifts smoothly 1st through 4th with no problems, but the OD does not appear to engage. I checked the OD solenoid, the relay, the eletrical connection and all are working but the OD will not engage and the car will not move in reverse. I drained the trans fluid, which was almost black and burnt smelling, hoping that this would help...but still no reverse or OD. Is the OD not allowing the car to move in reverse? I can "feel" the transmission shift into reverse and hear it whirl when I release the clutch, but the car won't move. Looking for some suggestions/help.