Speedometer gear recomendation
 

I just wanted to get everyone's thoughts on speedometer gear selection. I have a 1968 289 with a C4. I just installed a set of 3.55 gears. My rear tires are 24inches tall 14 inch rims.

My math says a 21 tooth gear would be best but I am being told a 20 tooth is best.

Anyone have any thoughts?

Re: Speedometer gear recomendation
 

Try the one that your math says is correct. Then test it next to a known correctly reading car. If you have to, you can then get the other one. They are only about $10 each. That's the way I did it.

Rev

Re: Speedometer gear recomendation
 

There is a formula to figure out what gear you need.....

ring gear x speedometer drive gear x tire revolutions per mile / 1000

this will give you the driven gear tooth number