Differential Upgrade

[toymachine595]

I have a '95 325is with an open 3.15. Im looking to upgrade but im not sure on fitments. From what car can i swap differentials from that would involve no modification. I have heard of problems with output flanges or something not matching up. So again im just wondering what can be easily swapped over to my car. I found a 3.45 from a 94 318 so maybe that will fit? If not how hard is it to swap over flanges. Any help is much appreciated.

[thekid]

You can't directly swap to a 318i diff. The drive shaft lengths and subframe mounts are different.

[nukeduster]

You can swap if you change the rear diff cover and the output flange, not hard at all, adds an hour to the job. Just gotta have a puller to remove the flanges.

Might as well upgrade to the m-roadster diff cover at the same time