2001 Chrysler TC speedometer quit working What could the problem be and how do you go about fixing it?

It may be the Vehicle Speed Sensor; here's how to replace it copied from another question. It also controls how it shifts. The Vehicle Speed sensor is located on the side of the transmission. You would be best to remove the battery tray and air intake plenum to see it. Trace the fuse block wire going to the back of the transmission. it will be located on the Left side (looking at the motor) after the ribs pointing back at you. It should have one mount screw and when you pull it out it will have a magnet on the end of the sensor. To replace the VSS, disconnect the electrical connector remove retaining bolt and it should fall right out. Simple once you see it. that's half the battle.