I have a 1966 Plymouth Belvedere ll 4 door sedan with the 225 slant 6 engine. My speedometer needle bounces. I have replaced the cable but what else do I have to do? Does it need to be lubricated, gearing replaced? Also I just installed a new fuel sending unit but I don't think the gas gauge in my instrument cluster is correct. Can it be needing lubrication like the speedo cable or is it something else? Thanks in advance for any insight.