65 Speedometer Cable and Gears

[orlowted]

OK - Thanks for all the great advise....I have deduced from the door plate that the axle ratio is 3:20. I have removed the original gear (or at least the one installed) and it was 16 tooth. The trans is the problem - I can not see any colors in the gears. I do not know where the trans came from, but I do have the number off it - C70R 7A040A

So what we have pieced together so far is
289 engine
3:20 axle Ratio
15x7 tires
4 speed top loader trans

If my eyes are correct in looking at the charts - I have a axle Ratio that does not go with this trans becuase I believe the trans is newer than the car and axle. Am I correct in assuming that the trans is from 1967 based upon the numbers? Yhat leass to another problem...It seems that depending on the axle ratio you have - it dictates the number of teeth. Are all the different number of teeth supposed to work with the gear in the trans?

I think I am really confused now. If the original one is a 16 tooth gear - is a 21 tooth gear going to fit any differently or work any better at getting the speedometer to stop jumping?

Am I barking up the wrong tree???


Help!!!