Unofficialbmw.com

[dale]

Not sure how widely known this info is on the E30 diffs is, so I'll just put a bunch of info down, maybe people will learn something from it.

E30 318i, M10, 1984-1985 : M168 ring gear, small case diff,
shared with 318ti, and Z3 with 1.9 engine

E30 325ix, M20 : M188 ring gear, medium case diff, viscous style LSD

E30 318i, 325, 325e, 325i, 325ic, M3, M20, S14, M42 : M188 ring gear, medium case diff, clutch style LSD
also used in Z3 with M50, E28, E24(83? and newer)
swap info: use an E30 rear cover, and E30 output shafts, which just slide in, and there are many medium case diffs that fit an E30.

In 1998-2002, the Z3 2.8/3.0 Coupe, came with a Torsen(similar to Quaife) style diff.
Gear ratios are:
2000-2002 Z3 3.0 Coupe, manual had 3.07, auto 3.46
1998-1999 Z3 2.8 Coupe, manual had 3.15, auto 4.10

If you like the diff ratio, you can directly swap one of these into your E30.
If you don't like the diff ratio, you can use a 3.23/3.46 and have 3.73 or 4.10 gears swapped on by a differential rebuild shop, and have a Torsen diff in your E30 for fantastic traction.
Also, you can use a 3.07 Z3 Coupe diff, and swap on 2.93 or 2.79 gears for ultimate Eta MPG and traction.

Ron Stygar has lots of information on putting a 3.46 Torsen diff into his MCoupe. Install instruction, parts, gotcha with the speedo trigger, all apply to the E30:

http://www.bimmerfest.com/forums/showthread.php?t=5078

This page describes how different types of LSDs found in various cars work, including a normal BMW clutch pack, and this Torsen I'm using:
http://www.houseofthud.com/differentials.htm


More info on a Torsen gear driven LSD:






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dale@unofficialbmw.com
sold in 2016
87 325 5spd eta

[dale]

A while ago when I was driving my '84 325e, I was looking for a mild diff upgrade, and found this 3.07 Z3 Torsen diff on Ebay.
Since 3.07 isn't a popular gear ratio, I was able to buy this almost-new diff for just a couple of hundred $$. New list price is over $2k.

Well I sold the 325e to Nick/Wazzu before I installed this diff into it, so I've been tripping over it in the garage for a while.

Recently I've been trying to get better MPG in my '92 325ic and thought I'd give this diff a try. Especially since my cabrio came with a 3.73 OPEN diff.

I got it installed last night and took it for a test drive in the rain. Wow! Very nice. The car isn't as quick off the line, no surprise, but 1st gear is actually usable again, where I've always felt it was on the low side before. You know, have to shift at 15mph or so.
Before in the rain, I'd always light up the inside rear tire when taking a right hand corner and hitting the gas, now the car just launches hard, very nice difference. If I really abuse the clutch I can get the back end to break loose, but I had no trouble in normal driving in the rain.

This diff may well have been brand new, it sure looks it, and it didn't come with a speedo sensor, and the one from my old 3.73 doesn't fit.

I've ordered a new one for $25 and it's on the way.

The stock E30 diff has a speed sensor that looks like the top one in this image. The Z3 diff with Torsen takes the lower speed sensor in this pic:
Ron Stygar figured all this out when he did the 3.46 Torsen swap on his MCoupe.


_________________
http://www.unofficialbmw.com
UnofficialBMW.com Webmaster
dale@unofficialbmw.com
sold in 2016
87 325 5spd eta

[idanity]

well done.

i was hoping someone would do this or with an electric conrtolled limited slip...

you make it sound easy...i hope i see a trend in lower prices and availibility...(and a test drive in your car)...im all set w/my 4.10 all done up, and it should last a lot of years to come, but its good to know, if i get another e30, about this option.
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[bimmerjo]

Nice post! also if you find a same year 5/6/7 (not 750) diff you can change output flanges/rear cover and they will work too.
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1988 BMW 635CSi - Black
1988 BMW 325iX - Grey - Soon will be black
1986 BMW 325ES - Black
2008 Kawi ZZR600 - Black
1977 Custom Deluxe - Red