after changing the engine on my 1996 750il i have experienced many problems including no drive from the auto box.i have the car on axle stands and when you run it and put in to gear the engine revs drop slightly (as if the gearbox is trying to work) but it will not turn the wheels even if you rev it, this happens in all gears, and sometimes the warning light for the gearbox will come on saying 'transmission failsafe program' obviously indicating a fault.but before i changed the engine the gearbox was perfect( i drove the car a few times) and even the semi-auto function worked! any ideas anyone?
it is hard to help you here, because this can be, many many problems way your transmission will not run.
To begin to locate the failure you need a scan tool to check the codes the come up after the installation. Also scan the car and read the codes ! The failure codes give you a Idea where the problem can be !