You can change the gear on the vehicle speed sensor (VSS), but they tend to get chewed up over time depending on the ratio/gear needed to correct your speedo.
You can buy a Speed Cal Speed Calibrator - SpeedCal at AmericanMuscle.com - Free Shipping! takes about an hour to install/set-up but worth it, you can change tire heights, gears, etc and flip a few switches to correct your speedo forever. Downside is $100 vs $10 gear.
Stan
I have the SpeedCal already installed. Used it well for my T5 and 3.73 gears. Problem is, it's not even in the ballpark with the TKO500. I hit 150 mph in 1st gear. So obviously the SpeedCal will not correct down that much. It's generally designed to increase the MPH reading when shifting from stock to a 3.73 or 4.10 gear set, and I need to go the other way.
I have a TKO-600 and 3.73 gears. The TKO's use a different speedo gear than T-5 tranny. I got mine from pro motion powertrain. I believe it is a red 23 tooth speedo gear for you.
I have the SpeedCal already installed. Used it well for my T5 and 3.73 gears. Problem is, it's not even in the ballpark with the TKO500. I hit 150 mph in 1st gear. So obviously the SpeedCal will not correct down that much. It's generally designed to increase the MPH reading when shifting from stock to a 3.73 or 4.10 gear set, and I need to go the other way.