It wouldn't be wrong at all if you find any GS6-X53 AWD gearbox for starters - but good luck with it - I'm looking for one too - if I find one I'm gonna buy it immediately. The problem about this tranny is that you have to move the N62 1.2 inch forward, to make it fit - and I'm a big fan of technical elegance - so the "cut and weld method" remains unwelcome. Anyways it would be even easier and cheaper, than to adapt the RWD tranny, as I did with my 4.6is.

The other option remains the quite common S6S RWD tranny, due it's very short and handy, compared to GS6. Still right now I don't have enough time to find a cheap source for fabrication, to keep the conversion costs on about the same level as the AWD-GS6 adaptation.

But I also toy with idea to make my Z3 V8 all wheel drive for fun.

So ultimately which one, GS6 or S6S, would be a better fit to handle high powered N62?

There's several variants of GS6, differing in housing by engine type, torque, TC type, RWD/AWD and gear ratios. So the obvious benefit of GS6-X53 is that you can couple it on ATC500, but taken from X5 or X3 they're to long to bolt on an adapter plate. We've let measured the GS6-X37 from petrol X5 and it was 3 cm or 1.2 inches to long, not to mention the "37"- versions of GS6 are to weak for N62.

So - the best solution for N62 powered X5 is the GS6-X53 gearbox, due it needs much less adaptation work, than RWD-only S6S; in terms of torque, the "53"-versions of GS6 should be even stronger than S6S-420G, which is also strong enough.

АХУЕТЬ! Video was awesome and of course one more Russian ??

That's exactly what I wanted to know. Which one would be able to handle power better. Looks like GS6-X53 it is! Now sourcing one is going to be quite a challenge.

Да,я тоже на 199 регион обратил внимание!
That 4.6 is a beast!
By the particular way of writing "дитя НЕ тешилось" I suspect one more russian capable user :D posting in another thread

Yes, I'm russian by nationality, living communting between Germany and Russia. But guys it's an american forum and I'd like to communicate in the way, understandeable for every user here. И без мата, пожалуйста!

When my tranny dies, and it will. I am very interested in this conversion - although it would be for a 4.8is.

Found 4 transmissions for conversion
 

Hey Dudes,

For you 4.8is guys looking for transmissions, I found 4. Car-Part.com--Used Auto Parts Market This is my coveted source that I found in case I needed to replace/rebuild mine..... but in the interest of helping this awesome project go forward, I have relinquished my selfishness. There is a nice one with 59k for 900 bucks.

They are all petrol 3.0 trannys, these have GS6-X37 mark and a 4.8 needs a GS6-X53 for the 369 lb fts of torque.

You also have to look for 335xi and 535xi manual trannys, which are also "X53" versions of GS6. Still I'm not 100% confident they will bolt on ATC500, due they're coupled on ATC300, but from the pictures the holes seem to overlap.