which diff should i use

[samstrimbu]

i have a 3.15 lsd diff and a 3.25 lsd diff and was wondering which one would be the best for my e30. im new at this so please help.

[vert_this]

which motor you using?

[e30slidewayz]

I'm assuming you're running an m20, sell both of your diffs and go with the 4.1 IS diff.

[dashboardmonkey]

If you have a g260 get an S3.73 or S3.64. Those diff ratios you have are pretty tall and will make your car slow but long legged.

[JTapper]

I have a 3.73 ring and pinion gear you can swap into one of your current LSD's fairly easily.

I went 24V supercharged and swapped in 3.25 gears into mine. PM me for details.

[samstrimbu]

yea i have the m20 in it. i had both of these diffs sitting around from my brothers s50 swap into his e30 m3. the other thing is that i dont want the revs sitting at 4000 rpm at 70 mph.

[mr.vang]

yea i have the m20 in it. i had both of these diffs sitting around from my brothers s50 swap into his e30 m3. the other thing is that i dont want the revs sitting at 4000 rpm at 70 mph.

if thats the case, sale those two and get a s3.73.

[e30slidewayz]

yea I agree, with the 4.1 its almost like you need a 6th gear

[e30rapidic]

are they e30 or e36 diffs? e36 diff won't work in an e30

[samstrimbu]

so i installed a 3.73 diff on my car the other day and have been driving it around and am pleased with it. it defiantly feels like its got a lot more pick up but the only issue is that while driving it to work the revs are sitting around 3500 rpm at 65 mph. now i normally wouldn't mind it but my new job is 20 min away via highway. the original diff was a 2.93 and at 80 mph the revs were at about 3300 rpm, so i think im going to put the 3.25 lsd diff in and see if the revs come down any more.

[MR 325]

All of these people should have asked you if it was an Eta or an i engine before giving advice.

The 3.73 is too short for Eta cars! I like the 3.25 with the Eta, it's perfect.

[Earendil]

All of these people should have asked you if it was an Eta or an i engine before giving advice.

The 3.73 is too short for Eta cars! I like the 3.25 with the Eta, it's perfect.

If it's a M20B25 with a redline over 6K, get the 3.73 and don't worry about the RPM being between 3K and 4K, the engine is happier up there anyway. The 3.73 was a stock diff for that motor anyway, trust BMW :)

If it's an M20B27 with a redline under 5K do what Mr325 says... even though his sig says he has a Turbo on his 2.7 "eta" :crazy:

[MR 325]

If it's an M20B27 with a redline under 5K do what Mr325 says... even though his sig says he has a Turbo on his 2.7 "eta" :crazy:

My bottom end is a 2.7L from a Super Eta. My top end... not so much. ;)

[Dirtboy]

yea I agree, with the 4.1 its almost like you need a 6th gear

Yup, I agree. I currently have a s4.10 in my car (325i). 1st gear is pretty much useless, lol.

Thanks to JTapper, I now have a 3.73 ring and pinion gear set that I may swap in...