E34 M20 Diff Ratio

[vtbimmer]

Does anybody know what the stock ratio is?

[Dan]

most are 3.73 if they are a 5spd. either locking or open also.
You can go up to a 4.10 or 4.27 if you want crazy acceleration.

[vtbimmer]

Originally Posted by Dan

most are 3.73 if they are a 5spd. either locking or open also.
You can go up to a 4.10 or 4.27 if you want crazy acceleration.

What is the reliability of used diffs? Is a 4.27 a huge notice in acceleration? Where would I lose power? Is there anything else I would need to do if I installed a 4.27 diff? Thanks for all your help!

[vtbimmer]

[Dan]

Originally Posted by vtbimmer

What is the reliability of used diffs? Is a 4.27 a huge notice in acceleration? Where would I lose power? Is there anything else I would need to do if I installed a 4.27 diff? Thanks for all your help!

Wow, I totally missed your last post, never got a notification. Yes a 4.27 would be a huge gain in acceleration, as well as traction with the LSD (limited slip differential). The only place you would lose would be up top, and fuel economy would also decrease. How do you drive the car for the most part? Highway? City? Track? These things will help me to recommend the best gearing possible for you.
check out the rpm/mph chart for the different ratios and that will help to direct you to where you would want to be. The purpose of gearing is to keep the car int he powerband for the majority of the time you are driving it.
I hope this helped.
If I for any reason am slow responding, please email me dan@diffsonline.com and I will reply asap.
-Dan

[vtbimmer]

I dont do any city driving. Most are routes 50mph speed limits. Usually doing 80 though. Some highway...just on trips. Never track the car but drive it that way. I've topped out @ 130mph but rarely see over 100. Feul economy is not a problem so Im thinking of the 4.27 What do you think? Should I upgrade the clutch if I install the 4.27? What else might need upgrading with the diff. change? Thanks again. Brent

[Dan]

Nothing else NEEDS to be upgraded when doing a diff change. That is the greatest part of a differential change/swap. You can increase your acceleration without affecting how the car actually runs.
The 4.27lsd sounds perfect for what you want.