ok, I'll explain this the best I can which won't be too great but here goes. The final drive is the 'gear' that the tranny gears grab onto. Every gear, 1st-5th pulls on this gear, so when you change your final drive, you make EVERY gear either shorter or longer. Basicaly, when you change your final drive the 'difference between' gears will not change they just all get shorter or all get longer. This is equivalent to getting a new rear end on rwd domestics. Someone please correct me if I'm wrong but this is how I understand it. The final drive on the gsr (and type r) is 4.400. To my knowlege this means that the wheel turns once for ever 4.4 turns of the ____________. flywheel? tranny gear? But then you have different gears in the tranny (1-5) so the number of rotations that the final drive gear turns per rotations of the tranny gear changes everytime you shift, obviously. I'm sorry, but that's about as much as I can help. I hope this clears atleast one thing up.

oh, and about the performance gains. Of course, the shorter your gearing is, the faster you will be able to acclerate. BUT it's not that easy. The transmission has to go from gear to gear efficiently, utilizing the powerband the best it can. This is why you dont go out and get a super short 1st gear, then you would not be in as high an rpm when redlining and shifting to second. Also, you shouldnt go and put a super short final drive in either, becuase then you will not be able to use your powerband long enough to lower your track times. Hope something I said helps.