After several months I finally found a machinist who could repair the messed up speedometer gear on my 1952 Chevy 3100. He used an 18 tooth plastic gear I had purchased that looked like the correct gear but the one piece plastic shaft that was part of it was too short. He cut the new gear off and pressed it onto my old shaft. My speedometer is now working but not very accurate. When it says I’m going 35mph I’m actually going 48, so it’s about 25% off. My thinking is i need the speedometer cable to spin 25% faster. I’m also thinking to do that I need a gear that has 25% fewer teeth. My current gear has 18 teeth so 25% is 4.5 teeth. If I bought another gear that had 14 teeth, would that get my speedometer close to being correct? Would it have a problem meshing with the gear inside my transmission that turns it?
