What can you do to calibrate your speedometer rear end was switched from stock in your 97 Firebird formula to a 373 out of a 2000 trans am?

To calibrate your speedometer after switching the rear end to a 3.73 gear in your 1997 Firebird Formula, you'll need to adjust the speedometer gear or use a tuning tool if your vehicle is equipped with an electronic speedometer. If using a mechanical speedometer, replace the speedometer gear with one that corresponds to the new gear ratio. For electronic systems, you may need a handheld tuner or a reprogramming tool to adjust the speedometer settings according to the new rear-end ratio. Always verify the calibration by comparing the speedometer reading to a GPS or radar speed measurement.