'91 318is Diff Question

[1990m3]

Having trouble finding the answers in the archive...what diff does this care come with? it's a 5-speed, not an auto...

Is it the large case LSD diff or the small case open diff? that's pretty much what I'm after.

Dave

[Rob]

there are opens and LSDs in both large and small cases. To know what yours is, look at the metal tag on the rear cover of the diff.

[redcarbon]

the 1991 318is will come with:

an open small case 4.10 differential or,

a limited slip small case 4.10 differential.

Mine came with an open 4.10, but I swapped in an LSD 4.10. Both small case, easy swap.

The e30 M3 came with a medium case 4.10 LSD, I believe, and it is compatible with the 318is, I believe, but don't quote me.

I think "large case" diffs are reserved for the seven series cars or something.

[Rob]

I thought for some reason some had a 3.91 LSD? Or is that like some autotragic something or other?

[1990m3]

alright let me rephrase my question. Will the 4.10lsd from my E30 m3 bolt right into the '91 318is? Or, do I need to swap out rear subframes to accomodate the larger diff that the M3 and 325's have?

I'm looking into a 318is to do an S50 swap, I'm trying to figure out which diff the car comes with as I'm making out a parts list of things needed for said swap

thanks

dave

[e30Matt]

Yes, the large case diff will bolt right into the 318is chassis. I know, my old 318is has an E30 M3 4.10LSD in it, and we just recently bolted a 3.73LSD big case into Spoon's car for the M50 swap.

[1990m3]

thanks for the info Matt,

Did the diff bolt right up to the 318 half shafts?