Speedometer Calibration

[DougA]

97 Tahoe,speedo is reading about twice what I'm driving,shows 50 when I'm going 25,anyone know what's causing this,and how to fix?Thanks

 

[KPOD]

97 Tahoe,speedo is reading about twice what I'm driving,shows 50 when I'm going 25,anyone know what's causing this,and how to fix?Thanks

How big are your tires?

 

[DougA]

Standard size tire thats always been on there,no tire change just happened suddenly.

 

[SunlitComet]

that is beyond a tire size change. is it consistent or a random change.

 

[DougA]

Does it all the time.What drives the speedo on these?Is it electric off the transmission?