[mickmate]

Unhook the speedometer cable behind the gauge and see if it spins freely on the cable inner or feels like it is hooked to the trans end. If it doesn't spin freely drive the car a little and see if the cable is turning. It may have disconnected at one end or the other or it may have broken. If the cable is good the speedometer can have a cable plugged into the back and it can be spun by hand to see if the needle flickers.