Fitting a large case diff to a 318is m42 flanges dont match

Post Tue Nov 06, 2012 12:40 pm

Fitting a large case diff to a 318is m42 flanges dont match, the bolt holes dont line up.
Does anyone recognise this flange type?
Does anyone know if the 325 or 318 diff flanges are different

also would an auto or manual make a difference?
[img][img]http://i1080.photobucket.com/albums/j33 ... flange.jpg[/img][/img]

Post Tue Nov 06, 2012 12:52 pm

Yep, small case and large case output flanges are different. You'll need the output flanges from your small case diff, if you still have it. Just lever them out with a big screwdriver or breaker bar

As easy as shown at 4:45 in the video below.

Post Tue Nov 06, 2012 1:01 pm

If you are just swapping the diff and nothing else you shouldn't need to change the output flanges at all?

The out put flanges are 'diff casing size' specific.

Only difference you should have is you need to shorten the prop slightly as a medium case is slightly longer.

I swapped a small case to a medium case earlier this year and it all bolted straight up as per the details above.

Post Tue Nov 06, 2012 1:09 pm

would it be better/easier to get 325 driveshafts?
i tried fitting the diff before and done as above changed the flanges from the small diff but they looked totally different like they were not going to seal properly.

Post Tue Nov 06, 2012 1:24 pm

What car did the diff come from?

E30 sourced diffs are interchangable as already written,but diffs from,say,E28 will need a flange swap.

E30 diffs have thick flanges(small case) and thin flanges(medium case)

Post Tue Nov 06, 2012 1:30 pm

all driveshafts are the same,the only exception being an abs type will have a toothed ring on the outer shaft .

your diff doesn't sound like it started life bolted to an e30

Post Tue Nov 06, 2012 1:32 pm

First of all, I assume it's a medium cased diff. (188), that you're fitting in place of a small case. A BMW large case diff. won't fit any E30 without major modifications, and is absolutely pointless without seriously uprated engine power.
The medium case output flanges stay with the medium case diff., and small case output flanges stay with small case diffs. Small case diffs, are narrower than the medium, so small case output flanges have built in spacers to make the overall assembly the same width as a medium case assembly.
All E30 driveshafts should bolt up directly to either diff assembly, without any modifications. If they don't, non E30 parts are being used.

Post Tue Nov 06, 2012 1:34 pm

how can i tell what car its come from?
it looks like a medium case diff with the 8 bolts on the back casing.
could i still use the internals?

Post Tue Nov 06, 2012 1:37 pm

What doesn't fit? I don't actually have a medium case diff. to hand to compare with your pic., but that looks like an ordinary E30 diff. output flange to me.

Post Tue Nov 06, 2012 2:04 pm

Duke137 wrote:If you are just swapping the diff and nothing else you shouldn't need to change the output flanges at all?

The out put flanges are 'diff casing size' specific.

Only difference you should have is you need to shorten the prop slightly as a medium case is slightly longer.

I swapped a small case to a medium case earlier this year and it all bolted straight up as per the details above.

My bad, I got confused as I have a mixture of E36 Compact stuff too.

Had to change output flanges on this medium case Z3M diff to fit E36 compact driveshafts. That's the small-case E36 Compact output flanges fitted. Got me worried now though, if anyone sees any probs with this, let me know!

Post Tue Nov 06, 2012 3:42 pm

More pics of the diff maybe someone can make sense of it?

[/img]

Post Tue Nov 06, 2012 5:30 pm

anyone?

Post Tue Nov 06, 2012 6:02 pm

I can have a look at my diff tonight, unless someone else can help in the mean time.

Post Tue Nov 06, 2012 7:11 pm

The flanges on my medium case (188) is 105mm diameter.

Post Tue Nov 06, 2012 7:38 pm

so the ones on this diff are wrong then as they measure around 113mm
Has anyone got an idea of what i can do to get round this problem or which car uses these flanges?
Is there a way of telling what car its come from?
everything else looks e30 the case backplate etc.

Post Tue Nov 06, 2012 8:29 pm

This pic shows my diff, the internal lip of the flange is round unlike yours which is shaped around each bolt hole.

This diff bolted in without a problem

Post Tue Nov 06, 2012 10:06 pm

can somebody measure from bolt hole to bolt hole for me please as it was the actual bolt holes which did not line up if i remember correctly.
would i be able to swap the flanges over for a 325 diff flange.
Anyone got any flanges they don't need?

Post Tue Nov 06, 2012 10:27 pm

I bet you have an E28 diff fitted with an E30 backplate, and still housing the E28 output flanges

Post Tue Nov 06, 2012 10:34 pm

i haven't got a clue, how u doing ravvy. remember me from the BBQ at builie dunno how u spell it. lol
can you adapt an e28 diff to fit an e30 by swapping the flanges?

Post Wed Nov 07, 2012 8:07 am

Easiest thing to do is buy the correct E30 medium case diff you are after, find out exactly what you have it and serve it on ebay to cover your costs.

That's what I would do

Post Wed Nov 07, 2012 8:22 am

TamTom wrote:i haven't got a clue, how u doing ravvy. remember me from the BBQ at builie dunno how u spell it. lol
can you adapt an e28 diff to fit an e30 by swapping the flanges?

Hi Tamtom, yes bud remember you and the rest of your gang well

Post Wed Nov 07, 2012 9:13 am

So can the flanges be swapped over?

Post Wed Nov 07, 2012 9:33 am

DHFiS wrote:This pic shows my diff, the internal lip of the flange is round unlike yours which is shaped around each bolt hole.

Correct, E30 flanges are round.

Medium case E30 output flanges can be swapped with the ones you have (they just lever out), but I'd recommend fitting new oil seals as well.
Don't replace the input oil seal, unless you know exactly how to do it before you start.

Post Wed Nov 07, 2012 9:57 am

any idea where i can pick up the flanges on a budget and the oil seals?

Post Wed Nov 07, 2012 10:12 am

Oil seals will be BMW or possibly ECP/GSF/Meatballs. Output flanges will be a wanted ad. on here, and hope that someone has a blown medium case diff. that they don't mind selling the flanges off of.

Post Wed Nov 07, 2012 10:18 am

TamTom, you also have the problem that the casing doesn't fit by the look of things, so either sell on your current diff and buy an E30 LSD, or locate a medium case E30 open diff and transfer the LSD spooler to that.

Post Wed Nov 07, 2012 10:52 am

The casing fits fine I've actually mounted it up all is good there.
It's only the flanges which don't match up.
Even the back casing is a direct fit!
Anyone know what flanges are interchangeable with e30's eg e36 flanges?

Post Wed Nov 07, 2012 11:56 am

E36 flanges are definitely not interchangeable with E30 ones as the mating face of E36 CV joints are a different shape.

Have a play around with various models on Realoem.com and try to match part numbers between models is all I can suggest. It's time consuming, but you will end up with an answer

Post Wed Nov 07, 2012 1:51 pm

I have a Z3 2.8 diff. in service on an E30, fitted with one Z3 flange and one E30 medium case one. The two aren't identical, but are interchangeable, on the Z3 case, at least.

Post Fri Nov 09, 2012 2:54 pm

Anyone got these? Need some asap

Post Fri Nov 09, 2012 3:33 pm

Brianmoooore wrote:I have a Z3 2.8 diff. in service on an E30, fitted with one Z3 flange and one E30 medium case one. The two aren't identical, but are interchangeable, on the Z3 case, at least.

Yeah sorry, I mean that E36/Z3 output flanges won't work with E30 driveshafts, Brian, you're perfectly right. They are perfectly interchangeable in terms of actually fitting the differential. Bet your setup would baffle anyone else who might take your car apart though!

Tamtom - finding flanges on their own can be hard work. Stick a few wanted ads up here and on E30Tech. Flanges + shipping from the US might be cheaper than resorting to buying a whole diff here (it was for me).