Our '04 chevy silverado is acting up. The speedometer is stuck at 120 MPH. The 4WD is not working also. The lights won't even light up on the control panel for the 4WD. What is wrong with the truck? I have read online that it has cost other people $500 to fix the speedometer. I want to know what is wrong. Has anybody else had this problem??
Sorry. I meant to add this...We have checked all the fuses and have disconnected the battery and it still doesn't work.

Have you checked the fuses? Or a sensor relay may be out.