auto trannies have filters, honda's we just drain and fill though. bmw's typically have gm transmissions, some of them have a green sticker that says LIFETIME FLUID and they don't recommend you change it, we have before it's just regular dexron/mercon 3. definately sounds like it's taking a long time for the shift solenoid to enguage with the source what they said low on fluid or dirty filter. more than likely even if you isolate the problem....unless it's a tranny mount which still wouldn't make it take a second to enguage in reverse...it sounds like that trannies on it's way out the door, so see what a replacement's gonna cost before you shell out the cash for this car with problems in half of the powertrain.