how do i know what ratio or what diff in me e30 bmw

[waddic 1]

what the title says

[Silver Fox 43]

Should be a tag under one of the bolts holding the back cover plate on.

[oscar90 0]

jack it up and check the wee tag on the back of the diff, will have ratio number on it... diff size you count the bolt or something, some who knows will chime in

[waddic 1]

was told i cant runa auto diff witha roatary becuase theratio diff. what is a manual diff ratio or number that i will need or what number does a manual e30 have.

[e30ftw 410]

Manuals have lower ratios like 3.46, 3.64, 3.73, 3.91 I think Autos had more like 4.1, 4.27, 4.45.

I guess it all depends what ratio you want to go for. With a high ratio diff from an Auto, the gears will be shorter, with a lower ratio diff the gears will be longer.

[BM WORLD 1286]

i would also change the diff and axles to the bigger medium case diff if fitting more power .