i have a 1991 750il and it has an open 3.64 gear ratio, and i seem to be getting 16.7 to 17 mpg all city driving which isnt too bad for me. but i would like to get a little more power down low. now i have an open 4.10 gear ratio diff out of a 1991 525i with about the same miles and i was wondering if i dropped the e32 diff and swapped all the brackets and cover and possibly the hubs?( what the axle shaft bolts to if the axle bolt pattern isnt the same) over to the e34 diff whether it would fit and would it make me happy as far as performance goes and the second part to my question is that i heard that if you want to put an lsd in the differential the ASC will not function properly. Thanks for all and any help.

i have a 1991 750il and it has an open 3.64 gear ratio, and i seem to be getting 16.7 to 17 mpg all city driving which isnt too bad for me. but i would like to get a little more power down low. now i have an open 4.10 gear ratio diff out of a 1991 525i with about the same miles and i was wondering if i dropped the e32 diff and swapped all the brackets and cover and possibly the hubs?( what the axle shaft bolts to if the axle bolt pattern isnt the same) over to the e34 diff whether it would fit and would it make me happy as far as performance goes and the second part to my question is that i heard that if you want to put an lsd in the differential the ASC will not function properly. Thanks for all and any help.

First, there's no way in the world I have a clue as to what would "make you happy"! :eek: :D :eek: So I have no answer for your swapping and whether it would even work or not.

But I do know that ASC & LSD can work together in the same car (my 91 735iL had both)...BMW included both options/features in e32s & e34s up thru the 1992 model year. It wasn't until ASC+T (included ABS braking) in 1993 that BMW began to drop LSD as an option on various models....them around the time the e39 & e38 debuted...LSD wasn't being offered even as an option on standard models but reserved its use on performance models like the M3 & M5.

There's a major difference between the two technologies...although BMW used the same button on BMWs equipped with this feature...see models below to determine when which system was used (I left out the 3 series & 8 series info):
ASC - reduces engine throttle when driving wheels detect slip
1990- 750iL
1991--92 535i/735i/iL

ASC+T - reduces engine throttle AND applies ABS braking to the driving wheels when wheel slip is detected
1991-up E32 750iL
1993-up E34 & E32 525i/iT/530i/iT/540i/740i/iL

i appreciate the info and im guessing mine has the ASC+T because it is a 1991 750iL so... im kind of still lost as far as that goes. and the making me happy i traded a 1990 535i 5 speed with a 4.10 lsd swap and the first gear was damn near useless, it revved out so quick i mean the car was descently fast it was chipped, cold air intake, single mass flywheel, 4.10 lsd... i guess i was more along the lines seeing if anybody had done this to their own 750il and whether they loved it or were happier with another gear set.

As far as I remember some people here have made such a mod or might be able to help you
http://www.bimmerboard.com/forums/e32/page/0

Erwin replied:
Your 750 has a large case differential, 210 mm ring gear, 8 bolts on the side flange holders. The 525 is probably a medium case diff, 180mm ring gear, 6 bolts on the side covers.

While maybe you can get the 525 case bolted into the car by swapping out parts (the 735s have med case diffs), it is weaker than the original. You'll be subjecting it to much more load than it was designed for: more engine torque, and a heavier car. Maybe it'll live for a while, I don't know. Just be aware of the potential for trouble.