how to get speedometer recalibrated?

[chopsknives]

Hey Thanx guys! Some good info here just shut down for the evening time to check this out! I'm wanting to get a tuner too! Thanx! She's a 2001 GM 8.1 gas w Allison tran. Sierra 2500HD 4X4

[Twist]

In that case you should be able to buy a hand held tuner and calibrate it on your own. Pretty much any LS1 based tuner should work, just go into the custom settings and input the range tire and wheel info.

[muzzlebrake]

Just add an app to the cell phone. Works off GPS and accurate