Rear Diff

[orr]

Can anyone tell me what diff i can put on my e30 m3, at the moment it has the standard 3.25 lsd. I have fitted an e36 m3 engine and box and all that side of it is fine but it is just reving to high on the motorway. Three and a half thousand revs at 70 miles an hour. First gear is only good for ripping your back tyres off, it is far too short and it will set off happily in second and spin the wheels. So what other diffs can i fit and what cars are they off, i have read that a 2.93 diff is good but do not know what car that is fitted to, any help will be appriciated thanks.

[ShepsEvo3]

I got a 3.15 diff from a Sport Evo/Evo2 but that won't help - much!

Good luck with your search.

[dasparkybad]

i believe you will find a 2.93 in a 528 auto e28
i am currently running a 3.08 from a e28 525 e with a 2.8 m52 engine and this is too tall but a lot better than the 3.63 i had before

[orr]

When you say to tall do you mean it bogs the engine down or its still revs to high

[DanThe]

Standard ratio on the E36 M3 is 3.15, your 3.25 should be fine

I have a 3.25 E30 M3 diff on mine with an E36 1:1 5th gear box and at 70 its just over 3000rpm, 225/45/16 tyres

[orr]

Its got 235/45/17 tyres but it is still 70mph at 3 and a half rpm thats too high for me it will use too much fuel, i might use it for tractor pulling

[oze30]

Your gearbox must be differnt to whats in a 535. I'm pulling just over 3000 at 80 in 5th. I'd kill for a taller diff!

Sheps, yours isnt for sale is it??

[dasparkybad]

still revs too high but not by much tested it friday night on m1 130 ish at rev limit in 5th

[DanThe]

Its got 235/45/17 tyres but it is still 70mph at 3 and a half rpm thats too high for me it will use too much fuel, i might use it for tractor pulling

Are you sure its a 3.25? Sounds more like a 3.63 to me.

I have 205/55/15 tyres at the mo and the rpm reads 3000 at 70mph

Diameter of my tyre is 606.5mm
Diameter of your tyre is 643.3mm

My speedo reads about 3 mph too high, so I am probably closer to 67mph

I reckon at 3000rpm you should be closer to 80mph than 70

[gareth]

diameter of the tyre won't affect the 'indicated' speed. the 'real' speed will change but the car won't know unless you have GPS!

[orr]

yes i have had the diff off and is says s 3.25 and i have turned it around to see how many times it spins and its the right one for the car