I have a project that im working on:
https://www.tamparacing.com/forums/m...3-project.html
it has a ford 9 inch rear end what is a good gear ratio to go with keeping in mind that i do not want to go 70-80mph in hwy and redline in 5th gear i have a 3.25 now
thanks for the help

 

Velocity (ft/s) = (rpm of engine x TIRE radius x 2 x 3.14)/(dif ratio x ratio for 5th gear x 60 sec/min) so just make your dif ratio "x", solve, using what the ratio of your current transmissions 5th gear is, and how fast you want to be going at that RPM. Remeber its in ft/s for velocity. pro tip: 60mph = 88ft/s. if you are clueless about your 5th gear ratio, MAZDATRIX for Mazda RX7, RX8, Rotary Engine Parts and Accessories has a great layout of OEM transmission & dif ratios for the 1979-1995 american RX-7

 

aaaand GO!

 

thanks for the great info