My speedometer is going crazy, what's the cost of repair? I leave in Illinois.

The GM cars use what is called a "Stepper Motor" for the speedometer, which can fail. They can be replaced, but instrument panel will have to be taken apart to do this. You can look this up on the internet and find where to buy stepper motors on E-Bay and also how to replace them on U-tube.

MIGHT BEE YOUR REAR AXEL SPEEDSENSOR LOCATED IN THE DIFERENTIAL REAL EAZY TO REPLACE . THE COST ABOUT $20.00

You'll need a rebuilt instrument cluster. The prices for the clusters are usually in the $250-350 range and about an hour to install it. You should have a local independent shop that can handle this.