Speedometer receives a signal from Vehicle Speed Sensor (VSS) located on transmission. Inspect for power source to VSS circuit, check fuse No. 7 (10-amp) for possible blown fuse. To inspect VSS disconnect VSS harness connector. Measure resistance between VSS terminals. If resistance is not approximately 250 Ohms, replace VSS. If resistance is approximately 250 Ohms, repair harness or connection between VSS and Instrument panel. Inspection of Speedometer ground should be inspected also.
I will agree with Protech2989....especially if you have driven through salty roads because of snow. Usually it is the harness because the salt deteriorates the plastic housing. When mine went bad, I paid $55 for the diagnostics and then repaired it myself. Get ready though because this is a costly item for such a small part and being an electrical part, I would not think of replacing it with an aftermarket part.