I have run the gambit, looking for my perfect ratio.
From 3.23 all the way to 4.44
. yea that was just an experiment.
I decided the 3.91 was the right fit for me.
You are not limited to E85/86 diffs.
Most of the shorter ratios I sourced from E83 X3.
Also some E46 will fit.
Do your research.
https://web.archive.org/web/20200622...GearRatios.htm