My 91 535i with 150k miles won't go in reverse...the gear doesnt engage. when the car hasnt been running for a couple of hours its fine but after 30 mins of driving or so, it wont go in reverse. i had the fluid replaced last year which resulted in the transmission failing (the gears wouldn't engage at all) so i had to rebuild... i think its time to dump this car. what do you guys think?