Small to Medium Case Diff

[MtechTone]

Right, not an E30 but an E30 rear-end, my car:



But unfortunately for my small case diff, I've stuck this in it:



I'd like to upgrade to a medium case diff, ideally from a Z3 2.8 or MZ3.

I'd just like to know what's involved going from a small to a medium case diff - how interchangable are they? Will I need to swap the rear half of prop and the 2 halfshafts etc etc.?

Any help would be greatly appreciated

Tony

[Brianmoooore]

Should be a straight swap, AFAIK, but what a waste! Get that engine out of there and into a shell that can appreciate it!

[daimlerman]

Never played with a compact,but small case to medium case on an E30 is straightforward.The bigger diff has thinner flanges to compansate for it's wider case,and the prop can be shortened at the centre joint to allow for the extra length.Just slacken off the large nut on the 'shaft and then use a 'Birmingham' spanner on the diff flange until it fits.

[MtechTone]

Never played with a compact,but small case to medium case on an E30 is straightforward.The bigger diff has thinner flanges to compansate for it's wider case,and the prop can be shortened at the centre joint to allow for the extra length.Just slacken off the large nut on the 'shaft and then use a 'Birmingham' spanner on the diff flange until it fits.

Oh really... I was under the impression that the flanges had a larger diameter on a medium case diff.

Sounds quite straight forward then. I better start looking for one...

Thanks.

[Jhonno]

Nice Compact

[MtechTone]

Diff hunting:

At the moment my car does 3k rpm at 70mph in 5th on the motorway, way too much for my liking. That's with the compacts stock 3.23 diff.

Z3 2.8 and MZ3 both use 3.15 which wont make a lot of difference really.

So does anyone know of a E30 type diff around about a 1:3.00 ratio? A 2.93 would be nice, but did any E30 come with those? Or is it possible to swap the diff covers on a diff from a completely different BM to make it fit...?

Help

[Jhonno]

Ive got a 3.25 with my ZF box and its 3.2k @70..

You can take the internals of a normal e36 diff and put it in your medium casing

[daimlerman]

I belive that E36 uses a gearbox with lower overall gearing,5th is 1.1 as opposed to E30 where 4th is 1.1 and 5th is an 'overdrive'...so on my E30,my 3.64 gives 75mph at 3000rpm. My project E30 touring with an M50engine/M40'box and a 3.35 diff I am expecting about 80mph at the same engine speed.So I have no easy answer for you other than to use a different gearbox....unless anyone else know different.

[MtechTone]

Cheers guys.

Really don't fancy changing the gearbox.

Is swapping over internals a diy job Jhonno? Could swap the internals of a stock E36 328 (1:2.93) into a medium case Z3/E30 diff...

[oldroydsr4]

I have a 328i sport as my daily and i think the 2.93 lsd if a little long for the car.

However on a resent trip to the ring it quite easily pulled it self on to 155mph down the autobahn.

If the cars is used on motorways alot then it will be great but imo if you like to have the ocassional play go for a 3.15 lsd.

[MtechTone]

I have a 328i sport as my daily and i think the 2.93 lsd if a little long for the car.

However on a resent trip to the ring it quite easily pulled it self on to 155mph down the autobahn.

If the cars is used on motorways alot then it will be great but imo if you like to have the ocassional play go for a 3.15 lsd.

Exactly I just don't know...

Swaying towards a 3.15 now to keep good acceleration, and it'd save me having to buy 2 diffs to make some hybrid diff...

[tomson]

A 2.93 would be nice, but did any E30 come with those?

I don't think so but certain E28's did and it just so happens I have one that is available in medium case form. PM me if you are intersted