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I recently started looking into why the speedometer doesn't work in my 78. When I pulled the cable from the transmission, I see what's i n the picture below. My questions are, shouldn't there be a plastic gear here? Does it just screw in? Why would the previous owner remove the gear, could there be something wrong with the drive gear? If all I need is a replacement gear, how do I know how many teeth I need? It's a 78 c3 with a 350 and 4 speed manual. Thanks in advance.
I have a 78 C3 with the L82 350 and 4 speed manual. It has a 20 tooth gear. I am currently looking at replacing it to see if the ticking sound coming from my speedo goes away. (There is a small chip in one of the teeth.) I am not sure if the number of teeth change between a L82 or normal engine.
The diff ratio is another factor. My diff ratio is 3.7.
You need to know what size drive gear is installed on the transmission shaft. If you have the fluid drained you MAY be able to see it if you look in the hole with a flashlight. I've never tried.
The gear will slip into that housing and have a rubber sleevewith a spring that acts as a retainer on the other end...unscrew the cable and you will see how it fits.
There are several websites that give a calculator to figure out what gears you need, but you need to know you're tire size and rear end gear. You'll also need to know what drive gear you have; as i mentioned before.
Last edited by Vette-kid; Apr 26, 2016 at 03:34 AM.
Speedometer gear questions
