E30 Zone

Whats the best rear diff for m52b28tu swap mine has a 1.8 auto diff in and it feel ok but is there a better option for normal spirted driving

There are a number of LSDs with differing gear ratios - try and work out what's best for your needs (based on whether or not you do a lot of motorway driving, etc.) from this list:

https://www.e30zone.net/e30wiki/index.p ... fferential

The lower the number, the higher the overall gearing will be. For most general purpose use, the Sport's 3.91:1 will be about right.

Thing I would be most concerned about is what size is the existing diff. Small case diff wont last long behind an M52 Go for a medium case and as above something in the region of 3.25-3.95 depending on gear ratios.

There are some good web sites to calculate this, depending on what you need/want

How doni know if my diff is small or medium, i cant afford an lsd at the moment but its on my list with rear disc conversion

Corasdad wrote: ↑

Sat Oct 18, 2025 5:57 pm

How doni know if my diff is small or medium, i cant afford an lsd at the moment but its on my list with rear disc conversion

Its all in the wiki
https://www.e30zone.net/e30wiki/index.p ... fferential

But if that is too much to read just count the bolts on the rear case 6bolts=small case, 8 bolts=medium case

Thanks