ok i have a 04 350z with a gtm turbo kit making 420 to 500 at rear. getting ready to build a Quaife Differential. so i can ether use the stock Manual 6 speed 3.538 diff or Auto 3.357 diff. i have both sitting in the garage. i use the car for auto x an a few track days. an i was thinking with auto x i find myself bouncing of the rev limiter more then i like too. so i could see where the auto could pick up a few mph with the different gears ratio. just not sure how the compromise at the lower speed if i would suffer.

 

stick with your ~3.5:1 ... if youre bouncing off the rev limiter that means you need to shift...

 

in auto x you will lose time with a shift. its rare to need third in most applications. at least it is around here. plus i know a lot of high hp cars switch for highway pulls.