A friend of mine picked up a new for cheap and the transmission goes into fail safe mode.

Previous owner had been in the transmission and said clutch packs are good.

Recommendations for diagnosing?

Availability of rebuild kits? Torque specs and tolerances for while I have it open?

(New to BMW transmission, but familiar with a lot of us brand automatic transmission)

Posting from a tablet... pardon the grammar. :-)

The BMW limp mod places the tranny in 3rd gear. Limp mode may be caused by any number of engine codes. You will need a good scan to determine what the problem is. My 535 did this after throwing an O2 sensor code. I replaced the O2 and the limp mode continued. I sold the car as scrap after a failed smog check and gross polluter result.

my 1990 750 had a gm transmission in it. they fail around 160miles but are easily rebuilt by someone with gm history

My by TH 400 internals. Check to see if it has a vacuum kick down or cable.

Somebody actually BOUGHT a 750?

ZF is REALLY proud of their parts, which are also fairly difficult to source unless you're an authorized ZF rebuilder.

The Cap'n

Yeah... he did. He's all proud that original msrp is so high.

I've been thinking about helping him fix it and sell it so he can pay off other project cars.

He just sent the info to me... i wonder if the 90 has same transmission as 99. ..

1999 BMW 750IL has 5.4L V12 5 speed automatic tranny rear wheel drive leather interior heated seats and steering wheel 5 disk cd changer tons of space

Might be simpler to source a used tranny and swap it.

So that the swapped in tranny can act the same due to the issue that is throwing the code that is causing the tranny to go into safe mode like Mike said. Make sure it is the trans and not just the computer being a dick.