M3 diff ratio question

[DaveM-sport]

S50b30 clutch will work fine with the E34 box.

For an Evo road/track car, I'd be using a 3.91 diff (build a 40-75% Evo LSD and use E34 M5 cwp) and a six speed box. That way I'd have good gearing down low but sixth would still be tolerable at 6-80mph

3.45/3.46 is about as short as you'll be able to go on it with the 5 speed without making it a pig to drive everyday if you do any bit of motorway speed driving. Depends what wheels and tyres your using too of course.


Still, with a 3.45... It'll go like scalded cat in a Compact shell

As for the rear axle, what would obviously be ideal is a Z3m rear end matched to Evo front hubs and brakes but at least fit E30 driveshafts as the Compact ones are pretty weak.

Small case diff if welded well will last reasonably well but you should be planning on fitting a medium case sooner than later.


For a medium case 3.45 diff, you'll need an E30 casing and something like an E34 520 cwp. 3.64-4.1 are all easily availible straight out of E30s but ratio might be too short for the road really.