Most of the problems with the Smith's speedometers are related to the grease in the actual speedometer drying out. I worked better twenty years ago also! I have had similar problems and been able to solve them by removing the speedometer and lubing it. It takes a little patience but it can be done. First remove the speedo and set it face down on a clean, flat surface. Carefully put a little oil; I use a oil conditioner called Militec but that's another subject, around the area where the drive enters the housing. Use a light weight oil. Emphasis on a little oil, you don't want it to overflow and mess up the face plate. Be patient, let it sit for a day or so and then do it again. Reinstall the speedo in the car and my bet is that it will work just fine. Second potential source of problems is the actual cable from the speedo to the angle drive. If lubing the speedo didn't solve the problem then you may want to try lubing the cable ie feed a little light weight oil from the top of the cable where it connects to the speedo. I believe the cable is factory lubed with a graphite grease which is less prone to drying out. I doubt the angle drive is causing the problem since it is strictly mechanical. Good luck!