the speedometer on occasion does not work correctly, it has reported the speed of the truck to be 20mph when it is not moving. It will also report this higher speed when traveling at 60 mph, yet you are really going 40 MPH. It has also reported speeds 20 mph less than what they are. Then at other times it report correctly, so as a driver you are never sure of your correct speed. While I have not stopped for this issue yet, I can see this happening.