Originally Posted by nuttybar08
Compare the IS-F's rear gear to the M3's 3.846
. I know why the M3 needs it (less torque), but what are the odds of getting a slightly more aggressive aftermarket gear on the F?
Near zero unless the IS-F starts showing up with the OEM differential in some racing series. The diff for the IS-F is unique among 2IS cars, and only the IS350 diff has the same bolt pattern to mount the unit in the rear subframe. I seriously doubt the IS350's diff is up to the task of handling the IS-F's input for the normal diff service life (300k miles) but you might could put the 350 piece in for a test. It's a 4.083:1 ratio, so it would make the IS-F a tire shredder.