I don't know all the details in my particular case yet. I just know that what started out as an inspection of the fairly common slow speed throttle take-up bank has turned into a trans replacement. My case may be somewhat unique in that I use my X to tow my 911 race car so on occasion I'll get the bang while pulling 4500 lbs behind me. There have been a couple of towing cases where the bank has been pretty violent because of the extra weight behind me.

What "codes" did they pull? I have no idea and didn't want to push the issue over the phone on a Friday afternoon before a holiday weekend because I knew the shop and the service manager had to be very busy. And I'll find out what "data" was transmitted to BMW tech support for them to reach the conclusion they did. But regardless of how they made the diagnosis, I'm getting a fresh trans. And it will get an annual dose of fresh fluid and filter body, just like I've always done with my previous GM tow vehicles. This "lifetime" fluid idea is just lame. There's no such thing.

FWIW- I used to be a BMW tech back in the 70's, that's how I earned my college tuition $$. Then I spent time as a BMW dealer parts and service mgr in the early 80's while racing a 2002 I built myself. These days, while no longer doing anything related to the car business (though I did consult to Harley) I spend my free time wrenching on the 911 race car, build my own engines and trans for it, and do all the work on my 528. But when it comes to these new auto transmissions, I will plead ignorance and let others do the work, especially under warranty. So if I use incorrect terms for procedures or tests, so be it.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R