Large (medium) case diff ratios - what has 4.something?

Post Tue Aug 25, 2009 8:40 am

As above, I'm trying to get a low ratio LSD. I have a medium case - 8 bolt - LSD but its 3.64, ideally I want one similar to the small case auto ratios 4.4 etc as its for a race car. Anybody know what cars/models these ratios came on (if anything) in the medium case size? If I can find an open diff I can likely make up a LSD in the right ratio using my existing one. Thanks.

Post Tue Aug 25, 2009 9:13 am

Hi

Us spec m3 4.1 also some 325ix tourings

Jason

Post Wed Aug 26, 2009 9:38 am

Thanks Jason, 4.1 like hens teeth then

. Anybody know if any other BMWs used the medium case diff with a ratio in the range 4.1 to 4.5, anything with an open diff would be fine it's just the innards with the right ratio that I need. Mebbe a 5 series from the same era? The guy I spoke to at the BM parts desk didn't know/didn't know who to ask to find out.

Post Wed Aug 26, 2009 11:08 am

E34 520i auto had a 4.45 I think and possibly the 525i auto. You may need to swap some parts from an E30 diff, like rear cover and output shafts. Someone else will hopefully confirm.

Post Wed Aug 26, 2009 12:18 pm

I sold a low mileage medium case 4.1 (from an American M3) for £350 and in hindsight that was waaaaay too cheap. They are rare as hens teeth.

It was an awesome diff for a 325i. Forget the hype about fuel ecenomy and top speed. Both were fine and the car was a rocket ship.

Jai

Post Wed Aug 26, 2009 7:13 pm

Hi

I got my 4.1 cwp for less than £150 from ebay.com

Jason

Post Wed Aug 26, 2009 10:46 pm

Jason that was a steal, good man. WillNZ I mean the bolts holding the diff back plate on. The 4.1s common on 318s and 320s are 6 bolt called small case diffs here. The mediums - 8 bolt here - are indeedy mostly 3.something, but its going on a 318is track car so ideally I'd like something not quite so tall. I was hoping a 325 auto may have one, but was way off the mark there. I'm off to ebay to hunt for an E34 320i auto being broken ...