M42club.com - Home of the BMW E30/E36 318i/iS

DISCUSSION => Engine + Driveline => Topic started by: serrano on September 14, 2008, 03:44:51 PM

Title: E30m3 Lsd
Post by: serrano on September 14, 2008, 03:44:51 PM

Quick question, does the M3 LSD unit fit bolt on to our 318is?

Title: E30m3 Lsd
Post by: tjts1 on September 14, 2008, 04:03:55 PM

Yep but theres nothing special about it. Just a medium case 4.1LSD. Same as 325i automatic.

Title: E30m3 Lsd
Post by: serrano on September 14, 2008, 04:12:00 PM

Thanks.
Almost all 318,318is,320,325 sold in Sweden were fitted with open diffs. LSD units are hard to find here.
I think this M3 LSD is a 3,25 according to this ratio table:
(http://img301.imageshack.us/img301/2872/diff2fi.jpg)

Title: E30m3 Lsd
Post by: tjts1 on September 14, 2008, 05:46:07 PM

http://www.e30eta.com/ecdiff.htm

Title: E30m3 Lsd
Post by: serrano on September 14, 2008, 06:10:26 PM

Hmm, says 3.25 here too: http://en.wikipedia.org/wiki/BMW_E30

Title: E30m3 Lsd
Post by: cecotto on September 15, 2008, 08:59:15 AM

I think the US M3 had the 4:10 ratio, as they have a overdrive gearbox

Where the Euro had a Close Ratio gearbox, and featured a 3,25 and 3,91 ratio as i remember.

Title: E30m3 Lsd
Post by: 1991318is on September 15, 2008, 02:51:28 PM

Quote from: cecotto;56718

I think the US M3 had the 4:10 ratio, as they have a overdrive gearbox

Where the Euro had a Close Ratio gearbox, and featured a 3,25 and 3,91 ratio as i remember.

Yep. Ours are 4.10lsd's in america.

Title: E30m3 Lsd
Post by: serrano on September 15, 2008, 03:12:23 PM

How much loss in acceleration am i looking at going from 4.10 to 3.25 with untouched engine? Very noticible, some or just?

The LSD is my second step towards turboconversion, which im going to perform this winter after i get my dose of snowfun driving. :)
The first step was the coilovers.

Title: E30m3 Lsd
Post by: tjts1 on September 15, 2008, 03:30:09 PM

Quote from: cecotto;56718

I think the US M3 had the 4:10 ratio, as they have a overdrive gearbox

Where the Euro had a Close Ratio gearbox, and featured a 3,25 and 3,91 ratio as i remember.

I stand corrected. I didn't know about the difference between US and Europe.

Quote from: serrano;56738

How much loss in acceleration am i looking at going from 4.10 to 3.25 with untouched engine? Very noticible, some or just?

The LSD is my second step towards turboconversion, which im going to perform this winter after i get my dose of snowfun driving. :)
The first step was the coilovers.

Not noticeble in the lower gears (1-3) and a lot in 4th and 5th. I went from 4.1 to 3.64 and any acceleration loss in the lower gears was more than made up for by the fact that I didn't have to shift as often. I picked 3.64 because it gets me to 100km in second only just. Thats how I think all cars should be. 3.25 would probably be a bit long for my taste but look at it this way. Your highway fuel economy will be stellar. Just use the lower gears more often and you'll be fine. Besides, if you don't like it, you can always sell an M3 LSD.

I put together this gear ratio graph to help me decide which diff ratio use swap. It doesn't include 3.25 but it'll help give you an idea of RPMs at different speeds.
http://www.m42club.com/forums/showpost.php?p=26477&postcount=28

Title: E30m3 Lsd
Post by: serrano on September 15, 2008, 04:21:08 PM

Thank your very much guys.