I am wondering if it matters what year the lsd comes from? I have the 4spd auto so from what i gather I should use a 3.91 lsd from an m5. I have found one from a 1988 m5 but I don't know if that will work? Any help is appreciated!

8eights can chime in here about the early M5 diff he recently got as to fitment. The ETK shows those years of differential as being the large case 210mm LSD (which is what you need) and 3:91 gears, but the case mounting appears different. I do know that the 3:15 LSDs from the early ('89-'91) from the 750i/il will mount up the same using the E31 rear cover and possibly flange exchanges.

I bought that Diff as a spare rcrad6653, It's in a crate, It was just a great deal, They are an awesome upgrade if you can get one, I mean night and day! I already had Lsd's on mines. Austin, The engine from that M5 would have to be a 3.8 to assume there's a 210mm Diff in the rear, Not sure if that was a option in 1988. I'm sure Mwrench or Wokke/Wolf would no, Good luck with getting one, You'll love it!

The question isn't just whether it's a 210mm or not, that's part of what's needed, but the case layout for mounting to an E31. I mentioned yours because it's from (what year M5?) and it was already in an 8er.

There should'nt be any difference? If it doesn't look the same it want fit! And the one i recently aquired wasn't in a 8er? It was bout to be installed but never got around to it.

this lsd that i found is on ebay and all it says is that it is 3.91 lsd from a 1988 m5 and it comes with a warranty. This tells me that it is safe to buy but again I have no experience with this and have only learned about doing this swap through the forums. I guess i should e-mail the seller and ask what size case it is?

The 1988 M5 would be a E28 and they had an entirely different case mounting and is not compatible with the E31.

The only M5 diff that is compatible is the US spec E34 '91 (that year only for a 3.91 US sped, Euro E34 M5 had 3.91 until '95)

The '95 Euro E34 M5 with the 3.8 engine had a 3.23 and a 6 speed.

Make sure you check which front input flange you have be cause that may have to be changed also but is not a show stopper.

Bottom line is the '88 diff will not work in a E31.

Ed, I have some 4 pot E23 front Calipers, Will they fit any of your cars?

What year and model? You wouldn't know what size pistons they have??

I am interested, shout me a PM and we can go from there.

Thanks for thinking of me!!