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Re: e28 M5/6 differential will not work in e31 850 (archive)
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Posted by Bert Smith on February 16, 2001 at 18:01:06:

In Reply to: Re: e28 M5/6 differential will not work in e31 850 posted by Greg K on February 16, 2001 at 17:37:20:


As far as I can tell, its a myth and the ASC actually works better with the LS units. I was also initially concerned after hearing the same rumors about conflicts and error messages, etc. But always from BMW mechs who never did the change. Usually the parts guys or service managers. Never anyone who had done the change.

So here it is... they exist beautifully together. IMHO, should have been equipped from the factory this way. The limited slip greatly reduces the occurence of ASC "light-up," likely due to the better (equal)distribution of power through the primary slippage areas: The rear tires. Particularly in the wet. If you do manage to break both rear tires loose, they'll be spinning at the same rate since they're "locked" by the LS unit.

I've also never received any error codes or other strange events after over a year of use, including playing with the system on the skid pad at BMW CCA events. In short, its not an issue.

Finding a unit is as simple as searching salvage operations for new arrivals. Here are a few sources, mostly in California, with recent 750 arrivals:

(1) 1988 750IL, Bavarian Auto Recycling, 916 635-4269,
(2) 1989 750il, Stockton Auto Dismantlers, 209-466-9531
(3) 1989 750il, Harout BMW Auto Parts, 818-834-8881 (these guys are pretty reasonably priced).
(4) 1990 750il, Riverside All Foreign, 909-276-9679
(5) 1989 750il, BMVW, Georgia, 770-969-999.

Good luck and make sure to have them confirm the LS with a silver stamping on the bottom of the case ("s") and "s" on the tag preceeding the 3.15 ratio markings.

Greg K


Greg,
I have a 91 850i 6 sp and want to do the diff swap. Mechanic here says the limit slip feature disrupts the ASC. Assuming this is inaccurate, advice on where I can find the diff.
Thanks
Rand
91 850i 6 sp silver/grey
Joe,

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


/
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

And one final note: don't even THINK about intstalling your used differential without an experienced tech inspecting the bearings!


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