off speedo question

[2k3silvergt]

I bought my 2003 gt used and it already had some stuff done to it. After a while I figured out the speedo was off. The faster I go the farther it gets off. Like if it says I'm doing 55 I'm running about 48 and if it says 85 I'm running about 70. Any possible suggestions to waht might cause this?

 

[COramprat]

Gears...you have 4.10's but no speedo adjust.

 

[2k3silvergt]

I'm not trying to dispute ur word or anthing but is that the only thing it could be, I'd love for it to be that but I still get 22 mpg in town on 93 with a heavy foot and about 28 on highway.

 

[9646gt]

I have the exact same speedo problem...and the car is oddly powerfull...it revs out pretty quickly and no matter what gear I choose for highway or city driving i only have to rest my foot on ghte gas to keep the car running at a set speed..its like i don't even have to press it..is it possible I too have 4.10's? Getting about 19mpg (give or take a few ) in the city..How much does it cost to fix the speedo issue usually?