Hi,

I've got a 1986 camaro with the original 85mph speedometer.

I'm working on the transmission, and it turns out the drive gear is missing.... so I can't count the number of teeth it used to have

So I did some calculations:
I have a 41 tooth driven gear, 3.42 rear axle ratio and 26" tires.

It turns out that the only driven gear that would work with my current setup is a 15.... but in order for that gear combo to be accurate, the speedomter would have to register miles at 1 mile per 971.45 cable revolutions.

...does that sound right? I thought most speedometers registered at about 1000 revolutions per mile.
If so, then the best combination I of gears could use would be a 45 and a 17.

Anyone know what the correct revs/mile is for these speedometers? 970? 1000? something else?

Thanks in advance for whoever knows this one. (or whoever knows where to look to read it off of the part)

-Masked

 

1000 turns per mile