Need help please. Need new gears for my speedo. Where can I find them 1991 electronic speedometer I brought the truck in to get some work done on it. I purchased the two small plastic gears. The mechanic said they weren't the ones I needed. He also said that he tested it and it is the speedometer that is broke not down by the transmission.. so I'm at a loss at what gear he is saying I need in the speedometer.