e36 m40 3.73 diff ring and pinion to e30 168 diff size?

[markus_74]

Hello,

Need some info.
I got some info here from local mechanic that there are 3.73 diff ratio from manual e36 318i m40? And he claim that he can install the ring and pinion gear into e30 small case diff?

Does all the info above is correct? Or it is not true?

Thank you
Markus

[Brianmoooore]

Not something I've done, but very probably true.
There's more to it than just swapping parts around, though. Needs specialist knowledge to set up the mesh of the gears and to shim the bearings.

[markus_74]

Thank you. I just got info that it is not 3.73 but 3.45, I think it is too tall

[Brianmoooore]

Yes, standard small case E36 diff. seems to be 3.45, which is too tall for an E30 with an overdrive 'box, and is the equivalent of around 4.26 when used with a direct top gear box, which is too far the other way.