I have an 02 Trans Am WS6 with a 4L60-E tranny, and it had 3.23 gears in it. It is about to get 2.73 gears in it and I need to know how to recalibrate my speedometer. Any info would be greatly appreciated.

 

This will need to be done in tuning with something like hptuners or efilive etc. You will need to program the PCM for them. The trans will not act correctly till you do and prolonged driving could do damage so needs to be addressed right away.