E30 Zone

Hi guys, to say that I'm confusing the heck out of myself is an understatement.

I have a 316 Lux touring (Woooohhh!) but, it needs more urge, to that end I also have a 328i cabrio e36 and the plan is to swap in the engine and box to the e30.

So far so good, now, I am looking to keep things sensible for road use and would like to maintain the 2.93 ratio of the original diff.

Obvious answer seems to be to put the e36 diff into the e30, but can't find a definitive answer as to whether it can be made to fit. The e30 of course has a small case diff.

Then theres the prop, it seems obvious that if the e36 can go in, I should be able to use the e36 prop...but that sounds way too easy! Is it?

I know the info will be out there, or come to that on here, but I find the search facility here really difficult to use and not throwing up what I need.

Call me names, point me in the right direction or better still, confirm what can or can't be done! Fank yew!

If you're using the E36 gearbox, you should use the E36 prop. That's”‹ the easy bit! With regards to the diff, the E36 box is 1:1 5th gear (unlike the E30 which has an overdrive 5th) so the E30 diff will be geared way too short. The E36 cannot be made to fit. Two options:
1) Source an E30 medium case diff and rebuild it using the innards of the E36 diff.
2) Source a medium case Z3 diff, which will be of a suitable ratio. This won't be cheap either though as Z3 2.5/2.8 diffs are 3.07 Torsen diffs iirc.

There is a 3rd option which is to source an E30 M3 diff (3.15 LSD) but that's obviously going to get ridiculous.

Thanks for the response Sir, the e36 prop will not fit the e30 diff flange as I understand it, or do I have that wrong? Is it just swapping the flange or is that again too easy?

Theres a diff on ebay at the moment but, I was under the impression (again) that the diff from other models needs to be the six bolt cover plate unit not an 8 bolt, does that hold true for a Z3 diff?

I think the 328 prop does fit an E30 diff flange? I can't confirm as I'm using a Z3M diff, but I'm sure someone else will be able to clarify that.

6-bolt unit is a small case, 8-bolt is medium case: http://www.e30zone.net/e30zonewiki/inde ... fferential

Either will fit but it's the 8-bolt plate you want if you're after a medium case. Same for Z3 diffs - the Z3 diff casing is identical to E30. iirc 4-cylinder Z3s were fitted with small case and 2.8/3.0/Z3M with medium case.

The only other thing that might be required if you use a Z3 diff is to swap the output flanges for E30 ones to fit the halfshafts. This is dead easy though, they just pop out with a bit of leverage and you can push the replacements in by hand.