E30 Zone

Whats the standard LSD diff gearing for a 318iS? I'm looking at getting an M3 diff which is 3.25 but wanted to know if this is correct.

Cheers.

the M3 diff is way to high for the 315iS, 325 would struggle unless fitted with an e39 or early dogleg box

in short, dont do it !

if its cheap, buy and stick on ebay

Yep, ive got an M3 LSD in mine cause it has the E39 box.
I think a 318iS is a 4.10 diff stock so thats a huge ratio difference!
Mind you i think a 4.10 LSD is even rarer! A few of the 318iS boys seem to have gone for the 3.91 325i Sport LSD if im not mistaken.

Right so lower number equals lower RPM per gear is that right? Therefore the gearing will be far too tall?

Yeah i think so, it depends on the gearbox ratios too! E.g the 3.25 LSD has ratios that are just about right on my setup, but wont be doing yours much good for its acceleration. I had a 3.46 diff at one point and first gear was useless and 5th would accelerate like a monster! Didnt make for a calm drive tho!

A cause for concern with a 2.7 running a 4.10 lsd then..

4.10 is standard ratio for the 318iS. You could go for either a 3.91, 4.10 or 4.27 ratio LSD and these are available as small casing diffs. The big casing diffs will fit but you are carrying around extra weight for no extra benefit.

whats a good combo for a 2.l then?

Thanks, much appreciated.

Are they a job and a half to fit myself?