I've done the swap on my 850 with a donor from a 750, both have an 8-bolt pattern. So yes, the 1988-1992 e32 750 works (as well as the e34 540 and M5).

I also have a 1988 M5 parked right next to my 8 in the garage. The M5/M6 differential unit is a whole different animal. Nothing at all similar between the two. Different mounting points on the casing, different rear cover, different speedometer sensor pick-up, different half-shafts, different input shafts. Two entirely different animals.

The 3.15 750 differentials are easy to find and relatively inexpensive. The last one I found for someone was a limited slip and the price was somewhere around $250 plus shipping (about $75 in the US by UPS).

Greg K

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Everyone,

I'm getting conflicting responses concerning which differential will fit a 91 850ia.

Is there any definitive information regarding the swaps that will work?

I'm looking at a '88 M6 diff (3.91) and want to know if this will work.

Thanks for the help,

Joe