Diff ratio options

[podiumprep]

Hi All

I am looking to change the gearing in our 325i sport 1989 E30. Running a standard diff I believe the gearing is 3.73, Medium casing (188). It also runs on 16inch wheels.

It is used for circuit racing so we would like to put a 4.10 + or more crown and pinion into the medium casing.

I have been told E28 and E36 gears fit, which ones and ratios I don’t know.

Anyone done this before?

Andy

[e30-EVN]

It would go like stink off the mark on a 4.1 ratio!! Busy through the gears but lively to say the least lol. I left my 4.1 2.0 diff on when I put m20b25 in my car and it was brill . Didn't really top it out but I would say it would only do about 130mph but get there quite impressively!

[Ant]

3.91 medium case LSD best option, 4.10 small case will last approx 1/2 day of abuse MAX

alternative is use a ZF gearbox with a 1:1 ratio from an E36, bolts up to M20 no issue. 081:1 in top for getrag you have now.

[podiumprep]

This is what we are after. So were did you get a 4.1?

[podiumprep]

3.91 medium case LSD best option, 4.10 small case will last approx 1/2 day of abuse MAX

alternative is use a ZF gearbox with a 1:1 ratio from an E36, bolts up to M20 no issue. 081:1 in top for getrag you have now.

Sounds intresting. So what model does the ZF gearbox come out of then?

Am i correct to say the e36 diff as same as the e30? Or is it just the C/P gears?

[e30-EVN]

In fairness ant I gave my car a feck load of abuse lol, infact I've hooked my m50 up to it just to get my car moving until I can source the right diff for mine! I'm after a 3.73 or 3.64......

That being said, track use is a little different to fast road but I di give her a lot of stick

[podiumprep]

Be nice if i could find a e36 crown and pinion to fit!

[teamalsoran]

i've got a 4.27 in mine, i robbed the crownwheel and pinion from a E34 518

[podiumprep]

i've got a 4.27 in mine, i robbed the crownwheel and pinion from a E34 518

What year was the car? auto or manaul? that sounds perfect!

How do you find gearing? ie does it top out?

[podiumprep]

bump on this

Still looking for a 4.1 Med case

[Grrrmachine]

Have you put an ad up in the Wanted section?

[podiumprep]

After some reading it turns out you can fit the E34 C&P into the E30 Med casing, anyone tried or done this? and with what ratios?

[Ajsingh]

I had my 2.7 running on a 4.10 diff and it was great fun! Off the line was real quick but it soon gave up and blew..

I now run a 3.91 LSD and its great! Haven't lost any off the line speed and its still great fun

[daimlerman]

Gareth will be able to build you a diff to your spec,pretty much,may well be worth a PM to him.

[podiumprep]

And what diffs we're they Ajsigh? Medium? Small?

Does Gareth know if E34's swap over then?

[daimlerman]

Does Gareth know if E34's swap over then?

Gareth will know how to build you a diff that will be difficult to break and give you the ratio that you need.

Some bits from other BMW diffs will swap into a case that will fit E30,but you really do need some specialist advice.....Gareth can offer this.

[Ajsingh]

Its now got a large case LSD. The 4.10 was a small case diff

[podiumprep]

So how do i get hold of this Gareth then, i couldnt find him in the menbers list?

[mrb27]

3.91 medium case LSD best option, 4.10 small case will last approx 1/2 day of abuse MAX

alternative is use a ZF gearbox with a 1:1 ratio from an E36, bolts up to M20 no issue. 081:1 in top for getrag you have now.

i raped my 2.7 with a 4.1 for about 6 months until it was sold, never made a peep and was RAPID!! lol

[gareth]

So how do i get hold of this Gareth then, i couldnt find him in the menbers list?

PM me

If you want a strong 4.1:1 LSD, you'll need to find a 188mm medium case diff (early E34's with small engines are the best place to start looking) and a E30 LSD.

I can then build one diff from the two.

Getting a good 3.91:1 LSD is the best option if you're on a budget but finding a good one is getting a lot harder.

A 4.1:1 diff in a E30 will only have been small case and it'll go pop if you've got any real power