Does anyone know of a speedometer calibration gearbox for a 1966 F100?
I have seen some online but they would not fit the speedometer cable at the transmission.
And my Speedometer was rebuilt and they used a new cable connection at the speedometer that snaps in instead of screws in.

 

I'd be pissed off if someone that was supposed to rebuild my speedometer changed out the connection. The screw on style is so much easier to deal with than the snap-on type, in my opinion. Oh well....

I don't know anything about a calibration box for our trucks, but there are adapters with gearsets in them that can help. Like this, for example, not that this one fits, either. But, these are generally to correct a wide discrepancy so you can get back within a range that the drive and driven gears can then calibrate to what is needed. Like if you go to much smaller or bigger tires, or a low or high geared differential is swapped in or things like that which can get you outside of the normal corrections available with just the drive and driven gears.

https://www.ebay.com/itm/Stewart-Warner-Speedometer-Gear-Reducer-Ratio-Adapter-GM/132444261399?hash=item1ed64b0c17:g:4LUAAOSwR2RaPqf O&vxp=mtr

This example is a 1 to 1.133 ratio adapter. As you can guess, a fixed ratio in a gearbox isn't the final answer to calibration so you might be referring to something else.

But generally the calibration is handled initially by the combination of the speedometer drive and driven gears. The gears come in a wide variety of styles depending on application and some are plastic, some are metal.

1966 shop manual volume 3 page 15-16

https://www.ford-trucks.com/forums/1...libration.html

Chad

 

You can try these folks. https://transmissioncenter.net/produ...y/ford/c-6/#C6 They used to have a lot of speedo stuff. It's been awhile since I have bought anything from them.