Originally Posted by Laurence

JCL has hit the nail on the head.

BMW treats the gearbox as a unit and will not try to repair the fault – as far as they are concerned, it is a sealed unit. Whilst there have been specific faults reported with certain types of gearbox (for example BMW had some failures of ZF gearboxes losing reverse due to premature failure of mechanical parts) a Trans Fail Mode can be caused by any number of things. If, for example, something as simple as an electronic solenoid failed, it would cause a Trans Fail Mode and render the whole gearbox as faulty and the car un-drivable. The BMW answer is to swap out the whole thing – where the solenoid itself could cost less than $100 to replace.
This is analogues to replacing an engine because a single sensor failed.

However, auto transmissions do wear out – it’s a fact of life. They have friction plates and by default these will wear and at some point will need replacing. The rate of wear will be determined by driving style.


A transmission shop that services and warrants a gearbox will (should!) replace everything that can/will wear, its time consuming and that’s why replacements are expensive.

I’m sure as the X5’s get older (and worth less!) more DIY capable people may be inclined to investigate the cause of their auto transmission failure. I would suspect that a greater number of the (low mileage < 100,000) failures are caused by electronic faults than mechanical ones.
And remember, all the electronics can be accessed from the bottom of the gearbox without removing it, indeed the whole valve body assembley can be removed with the gearbox in situ. I for one will be looking there first if/when my gearbox &quot;dies&quot;!