Originally Posted by 67SATisfaction
Are switching speedo gears the only reliable way to adjust an inaccurate speedo?

I'll use the calculator chart above to get an estimate of what teeth count I need with 225/70-14 tires and a 2.76 rear.. then compare to the current speedo gear in the car..

The speedo in our '65 with cable-shift 727 automatic is off by about 10% too fast (reads 90mph when actual is more like 80).
So if I count the teeth on the current speedo cable gear, I figure I have to find a replacement with 10% fewer teeth. is that how this works?

Thanks,
- Art


That chart is not accurate for the 65 style speedometer pinions.

Conversion to modern tire sizes

Snipped from the 65 Plymouth FSM

Looks like you need a 17 Orange pinion, assuming you don;t already have that. The coverage spread is kind of wide. Brewer's has used, $80.


pinion.JPG
Last edited by Sniper; 06/30/19 02:54 PM.