Great set of pics. I did this swap on my '92 850i. auto, Supersprint exh, Comforti chips. I did a few runs with the g-tech pro meter for both 0-60 and 1/4 mi before and after, on the same "test track" in sport3, ASC off, brake torking from the same RPM, 1/4 tank of gas acording to the guage, and I found the times to be identical. It was however 5-10 degrees warmer durring the after runs. I had planned to do more runs when it was the correct temp out, however I never got the chance.
The ratio change is only 7%, and much more is needed to make a noticeable change. On the freeway for instance, the rpm change is around 200 RPM (if I remember correctly) so just imaging what the car accelerates like 200 RPM higher (5HP maybe) and decide if that is worth the change.
You will need the special oil from BMW or equivilant and I found mine made a terrible racket when turning. I added a bottle of special posi lube, (don't know what it is actually called, mine was what Ford uses) and after a few miles it quieted down.
I wouldn't do it again. $450. for used M5 rearend, $300. shop labor.
