freddy4099

I have a 1979 C3 with a speedometer drive gear problem, I have traced the speedometer cable all the way to the transmission and can turn it by hand and see the speedometer on the dash turn. I pulled the gear it in it, and it had 22 teeth and was like a cream color it worked for a while but was stripped out and reading 10 miles per hour faster than I was actually going. I replaced it with a yellow 24 tooth gear and it was reading about 5 miles per hour faster than I was actually going but then stopped working after only 5 miles. When I pulled it was totally chewed up and stripped out. So, here is my question, do I need to take it in to a transmission shop and have them replace the gear that turns the speedometer gear or could it be something else? I ordered the yellow 24 tooth gear from Chevrolet and it was made to be used in the TH350 that I have. thanks for the help.

0Willcox Corvette

You probably exceeded the mesh of the drive gear by going to a 24 tooth driven gear.

If you look at the chart below, you should be able to figure out what combination is correct for your car. If the car is a automatic then 22 tooth is the only driven gear listed and used a 8 tooth drive gear. I think the 22 is the largest gear you can run with the 8 tooth drive.

freddy4099

That chart helps a lot thank you much, only problem is, with the 22 tooth gear the speedometer reads 10 miles per hour over the speed I am actually going.

thegazman

Change your drive gear. I have a 1979, L-82 with a 3.36 differential. A transmission specialist recommended a 10 tooth drive gear and a 21 tooth driven gear. My drive was worn down so I installed a new 10 tooth. Speedometer works smooth and accurate with the new gears.