Diff fitting question

[BONNARSKI]

Will a diff from a 1986 E30 325i Sport fit my 1990 E30 318i Touring without having to change the output flanges?

I'm asking as i know the Touring has rear disks and the bigger 51mm front struts so are the drive shaft flanges the same as the 325?

[Andyboy]

Yes, it'll fit fine but ther ratio will be very tall. Whilst the flanges are different, the distance between the driveshafts is the same, i.e the total diff width with flanges is the same on both. Where you will have to alter something is the prop length because the big diff is slightly longer. Easily done though; you remove the exhaust heat shield, slacken the collar nut on the prop just behind the centre bearing and tap the end of the prop with a mallet to shove it in on the splines a little. Bolt the new diff on (it can be a bastard to get the four bolts in - do them all few turns and jiggle the diff about until they are all in - then tighten fully) and then bolt the prop up before retightening the collar nut.

The 318i diff is a 4.1 ratio and the 325i will be either a 3.64 or a 3.73, both of which are a fair bit taller meaning less revs at speed but fairly sluggish acceleration.

[BONNARSKI]

Thanks for that lad, thats exactly what i was looking for.

Your right about the ratio's being taller, i'm trying to get better MPG as the M40 is drinking fuel at a mad rate and i can't find why. I have the diff here so thought i'd try that plus the addition of the LSD would be nice lol.

I've been told it could be the FPR is done but can't get one about where i live. The car just doesn't seem right to me. It accelerates fast and pulls good so the taller diff wouldn't slow it down too much for my liking. I drove a Mk4 astra DI estate before so as long as it's not as slow as it i'll be happy lol