M3 LSD - Big or small case?

[Jhonno]

Just put an M3 diff on my car.. is it a big or small case diff?

[Jimbob]

What size was it in comparison to the one you took off?

[E30Adam]

6 bolts on cover = small
8 bolts on cover = large

[Jhonno]

did they do a small case m3 diff then?!

[E30Adam]

did they do a small case m3 diff then?!

If not then you just answered your original question mate!!

[Demlotcrew]

Only Big case!

A

[Jhonno]

thats what confused me.. i didnt think they did but the diff i took off my 316i was exactly the same size as the m3 diff i put on. No messing with prop lengths etc..

[Toby_Unna]

Dan do as Adam says and count the bolts on the rear cover.

either your 316 had a big case diff on for some reason
or you don't have an m3 LSD

count the bolts and you'll have an answer. 6 bolts small, 8 bolts large.

[Jhonno]

yeah i'll count..

thing is its deffo an LSD and its v long - i can get 50mph in 1st now

[Jhonno]

Looks like its a small case then... 6 bolts

it had a different speed sensor on the diff, i had to put mine on as it was a different connection

now im confused.. what the hell is it from? it has S3.25 on the tag

[M3Compact]

Looks like its a small case then... 6 bolts

it had a different speed sensor on the diff, i had to put mine on as it was a different connection

now im confused.. what the hell is it from? it has S3.25 on the tag

Are you sure Jhonno? 6 bolt diffs are usually low ratio.

This is an 8 bolt, large case diff.

[Jhonno]

my filler holes dont look anything like that...


its deffo v long ratio - 2.5k @ 80mph

just over 50 in 1st gear and 80 in 2nd

[M3Compact]

my filler holes dont look anything like that...


its deffo v long ratio - 2.5k @ 80mph

just over 50 in 1st gear and 80 in 2nd

Deffo LSD too?

[karlp]

I have an E30 M3 LSD in my garage with a 3.25 ratio and it is definately large case.

The only difference to a 3.91 I bought from Rearwheel Nick is that the output drive flanges are different. The M3 have a thicker flange.

I can take measurements if you like.

Karl

[Jhonno]

my filler holes dont look anything like that...


its deffo v long ratio - 2.5k @ 80mph

just over 50 in 1st gear and 80 in 2nd

Deffo LSD too?

deffo an LSD - turn the input and both outputs turn the same way, also checked with car in the air, turn one wheel the other turns the same way.. in neutral

also went down to a local dirt carpark and everytime both rear wheels spun up exactly the same

[Jhonno]

I have an E30 M3 LSD in my garage with a 3.25 ratio and it is definately large case.

The only difference to a 3.91 I bought from Rearwheel Nick is that the output drive flanges are different. The M3 have a thicker flange.

I can take measurements if you like.

Karl

that would be cool

also any pics of the cover plate?

[karlp]

Just taken 3 pics - how do I post picks or give email.

Karl

[Jimbob]

go to www.imageshack.us - very simple to use mate just go on there and you'll have it hosted in 2 mins, you just need to copy a line for each pic on to the zone and it'll show it ;)

[karlp]

Pics posted here

http://photobucket.com/albums/b167/karlp10/?sc=1

Karl

[Jhonno]

Looks different to mine.. give me a couple of mins and i'll put some pics of mine up..

[Jhonno]

Not the best of pics but it was on my phone...

[karlp]

That is not an M3 diff - it looks like a small case .

Notice how it is relatively straight from front to back whereas mine has a bulge.


Karl

[Jhonno]

thats what i thought from looking..

small case is not gonna be up to the task of an S50 really is it?

damn it

[M3Compact]

small case is not gonna be up to the task of an S50 really is it?

NO

Fancy swapping it for one that will be?

[Jhonno]

YES!!

[M3Compact]

YES!!

What ratio are you looking for?

[Jhonno]

erm... 3.25 or even 3.15

[pacerpete]

Jhonno , i'm guessing that diff you have is out of an early e30 323i dogleg car, hence the tall ratio ?.

[jonb]

sir pete is right, 323i diff. i had one of these on 325i a few years back, before my trading days.

they are as weak as any other small case diff. this lasted about a month. and cost me Ԛ£250.

[Jhonno]

Ahh.. thank you Pete/Jon

At least its rare and working

[Andy335Touring]

Thats a shame as i was mulling over a swap to a 323 3.46 dif for mine, poxy small case difs

Is there a big case E30 3.46 ?

http://www.behindmatrix.com/e30/fotost/ ... f00023.htm

[Andyboy999]

323i had the small case diff until about June 1984. After that the big diff came out with the 325e 9Eta) and this is in fact an E28 518 - 528i casing with a different rear cover - it's called the Type 188 and was also used on the lower powered E34's. later 323i, 325i, 325e and M3 all used the big diff.

As for the strength of small diffs, a good analogy is Pacerpete's trousers. They're too small for his arse which is why the greasy crack can often be seen poking over the top. He doesn't have that problem when he wears a dress.

[pacerpete]

F.A.O Andyboy, the reason my jeans dont fit is because lidl dont do xxxxxfcnt size and as for wearing dresses i wish !, none of them ones you lent me Andy fit !

[Andy335Touring]

323i had the small case diff until about June 1984. After that the big diff came out with the 325e 9Eta) and this is in fact an E28 518 - 528i casing with a different rear cover - it's called the Type 188 and was also used on the lower powered E34's. later 323i, 325i, 325e and M3 all used the big diff.

Cheers for the info Andrew

Could i combine the parts from an open 3.46 dif with the LSD unit from my shagged M3 dif to give me a 3.46 LSD dif ?

It's good to see the return of the Andy/Pete banter,such a good laugh !

Pete, did you get my PM ?

[Andyboy999]

F.A.O Andyboy, the reason my jeans dont fit is because

......he hasn't bought any new ones since he started to restore a Triumph Spitfire in the mid eighties. Apparently it's a Man thing. A bit like breaking metal bumper 325i Sports!