M30 + small case diff?

[kdevitt]

Am working through an M30 swap at the moment and have a diff question.

The diff on my car is a small case LSD, think the ratio is 3.25 or so. I'd be happy enough with the ratio - just wondering has anyone run a small cased one on their swapped E30 and had it last more than a week?!?

Currently looking to swap it out for a medium cased one but just curious as to whether or not I actually need to.

Cheers

[jimbom30cab]

Yes, i ran a small case 4.1 initially, it was fine. If it's for normal sprirted driving i'm sure it will be fine, track use would be a different matter though.

Small case 3.25 LSD must be a rare diff though, not heard of those before

[zaust]

Ratio is good, keep it or swap with me I have a med 3:46 lad.

[kdevitt]

Not 100% certain on the ratio to be honest - anywhere I read says an 83 323i auto had a 3.25 diff, but that's an open diff. Just checked spec sheet and it didn't help either.

[maxfield]

This is Gareth running a small case diff at pod..

IIRC

[kdevitt]

This is Gareth running a small case diff at pod..

IIRC

Brilliant - a picture tells a thousand words!

[kdevitt]

Build sheet says

S209A SPERRDIFFERENTIAL 25% Differential lock 25%

Think I'll be selling it on and going for the medium case anyway.

[jimbom30cab]

I have a 3.46 in my M30 and i think it's just pefect but most of my driving is motorway. If you are a country lane demon you might want a 3.64 or 3.7x

[kdevitt]

3.46 would definitely suit me perfectly - just keeping an eye out for one now.

[jimbom30cab]

cool, iirc with the 3.64 on 15"BBS and the e34 manual box then 70mph is just 2550rpm so nice and wafty.

[gareth]

This is Gareth running a small case diff at pod..

IIRC

Brilliant - a picture tells a thousand words!

Haha, that was 6.5 years ago! Good memory!

Here's the link to the gruesome damage.
http://www.e30zone.net/modules.php?name ... postmortem
So in short, NO! Don't use a medium case diff with M30 torquesss!

[maxfield]

Gareth - I can remember it like it was yesterday. Didn't realise it was that long ago tho

[gareth]

No... Scary or what! I had a look at my logbook the other day, i've owned my E30 for 9.5 years! WTF?!

[kdevitt]

So out of interest - where are people sourcing their medium 3.46 diffs from? Seems that the prices have gone nuts in the past year.

[mccarthy]

I recently picked up a e28 3.46 diff and swapped the output shafts and back plate. Works perfectly and find a good ratio for the m30

[BoostED]

I currently have a small case on my m30b35 turbo...

[gareth]

I predict bad things!

[maxfield]

See above

[rob0r]

I'm currently running (drifting) a small case with my E28 M535i Motronic 1.3. All good so far, though I will be going medium case and when I can be assed!

[gareth]

When you say small case on the E28, do you mean 188mm? AFAIK the small (168mm) case wasn't used on the E28, just 188mm and 210mm. The E30 got 168mm and 188mm.

So 'small' on a E28 is 'large' on a E30. Or more broadly speaking, both are 'medium' case!

[rob0r]

I put it very confusingly! I meant E28 M535i engine running motronic 1.3 inside my E30 (extra bhpz)! Which is running a random E30 small case.

[gareth]

Ahaa, makes sense. In which case I refer to my previous comment!