| This calculator
gives you a graphic display of the miles per hour your vehicle will
be at when your present transmission shifts to the next higher gear.
It then compares the results to the three popular GM overdrives.
The engine rpm limit where these shifts will occur must be set by
In the top
box, choose your present transmission from the drop down menu,
enter either the P-metric size or actual measured size of your
tire, enter your rear end ratio in decimal format (ie: 3.73),
set the rpm limit and click "Calculate"