3.64 or 3.73

[D3R3K]

I recently swapped my auto 325es to a m20b25 engine with a manual trans. The car currently has a 2.93 and I feel like I can’t get out of 2nd gear on the back roads. I have a 3.64 and a 3.73 gear set. Which would you recommend. The car will be mainly a fun car to drive and maybe a track day or 2 a year.

[It's Soda Not Pop]

3.73 for that power level. 3.73 on the hwy isn't bad either. I also make sure that they are a LSD.

[lukeADE335i]

Agreed - the 3.73 is what the 325i came from the factory with.

[Vincenze]

There are calculators that you can use to compare differential ratios.

https://www.google.com/search?channel=fs&client=ubuntu&q=e30+diff+calculator

[Vincenze]

The car currently has a 2.93 and I feel like I can’t get out of 2nd gear on the back roads. I have a 3.64 and a 3.73 gear set.

You can't install a 3.73 gear set into a 2.93 differential.

[D3R3K]

You can't install a 3.73 gear set into a 2.93 differential.

Why’s that? They are both for a medium case diff.

[jsta1109]

Why’s that? They are both for a medium case diff.

The carrier offset changes from 3.07 to 2.79 meaning any ring gears from 3.15 up won't fit. Racing Diffs sells a "differential crown ring spacer" that allows you to adapt but depending on price you'll probably be better off purchasing a complete diff with the correct ratio.

[D3R3K]

The carrier offset changes from 3.07 to 2.79 meaning any ring gears from 3.15 up won't fit. Racing Diffs sells a "differential crown ring spacer" that allows you to adapt but depending on price you'll probably be better off purchasing a complete diff with the correct ratio.

Thank you!

[82eye]

The carrier offset changes from 3.07 to 2.79 meaning any ring gears from 3.15 up won't fit. Racing Diffs sells a "differential crown ring spacer" that allows you to adapt but depending on price you'll probably be better off purchasing a complete diff with the correct ratio.

that is new to me as well. i've harvested / rebuilt ls units before and changed gear sets. that is good to know about the 2.93.

[Panici]

I vote 3.73 LSD as well. Works great with the Getrag 260 ratios.