What diff size is this?

[Coyote_ar]

This is my E30 320i 1984's diff. Is it a small case or mid case diff?

[oze30]

I'd say its a small.. though could be wrong. Looks like its got 6 bolts. Anyone else?

[eta]

I believe the diff on the 520i and 320i are interchangable which will make them medium case.

[Coyote_ar]

honestly im a bit confused. some people state that the 320i has a small case diff. other people say all 6 pot cars had the medium case diff.

anyone has a pic of a medium case diff so i can compare both? so far all the mid case diffs i found while googling, had the Z3 cover, so that didnt help.

[StuBeeDoo]

Looks like 6 bolts holding the rear cover on to me so it's a small case.
8 bolts = what you're calling a "medium" case.

[oze30]

Looks like it got less fins from a medium case from memory, the medium case has fins across the bottom L-R. This doesn't. It has 4 fins.

ALSO from the 2nd pic, it has 6 bolts.

6 bolts = small case!

[Coyote_ar]

i see, thanks guys. will this diff be able to support a M20B25 engine? no mods, just a simple 2.5 engine.

[eta]

Sorry I was wrong it is a small case it mounted differently.

[gareth]

it looks like a small case to me. the body on the large case is wider, though the distance between the driveshaft flanges is the same. on a large case diff there is a 1/2" gap between the flanges and casing, small case is nearer 1 1/2"

depending on how you drive, a small case could be ok. i destroyed my small case one very easily with my 3.5 M30. iirc, Kos did the same with his 318is

you'll probably want a taller final drive with a M20B25 too so i'd swap the diff with a medium case one.

incidentally, there are three basic sized of bmw diff. E30's had small case and medium case. the large case is only availible on 5's and 7's etc. confusingly a lot of folks call the E30 medium case diff a 'large' case.

[Gunni]

Small case = one bolt on the bottom of the cover
Mid BMW case = two bolts.