Quick Question

[Elwood4u]

I was hoping you guys could help me out. I bought my stang last fall and the previous owner did not tell me if he had put gears in it or not.
So what i did was at 2500 rpm's I was doing 61mph in 4th gear.
I was hoping someone knows how to calculate it final drive ratio to tell me what is in the car.

 

[dsrtdukone]

Must know your wheel/tire size to properly calculate.

 

[Got Boost?]

heres the equation

axle ratio equals: (rpm x tire diameter) divided by (MPH x 336)

 

[Elwood4u]

my tires are 255/40/17.
do u mean circumference?

 

[Got Boost?]

no, tire diameter .... poeple who race know that slicks are measured in diameter.....my guess for the diameter of that tires is probably 26 but i dont know....