So I started realizing that when I'm doin like 5 over the speed limit, everyone is zooming by me. So I had the wife drive in front of me and find out that my speedo is 9 or 10 mph off (She doing 70 mine reads 80). To the best of my knowledge its the stock gears, certainly doesn't feel like lower gears (Anyone from Tampa wanna do comparison sometime?) Anyway, question is, do I have to buy a tuner to get my speedo correct? Don't get me wrong, I would love to have one but gotta wait for the funds to come available.

Edit: wheels/tires are stock 17" rims with 245/45 sumitumo (sp) which I'm pretty sure are stock size, correct me if I'm wrong.

 

to tell if it is the stock gears you can jack the car up and spin the dirveshaft and count how many times it takes to turn the wheel one revolution example you spin the driveshaft 3 times to 1 revolution of the wheel axle ratio is 3.00:1 now the stock axle ratio is 2.73:1 for auto and 3.27:1 for maunal hope this helps

 

^ correct

To calibrate the speedo you need a tuner to input the tire diameter and final gear ratio (rear-gears)

Jazzer

 

I believe that on the new-edge models both the manual and automatics came from the factory with 3.27:1 rear ends--I know this is true for the '03 and '04 models, and believe it's the case for '99 through '04. The '03 Mach 1 had 3.55s...