Two Speed speedometer adaptor

[69Ford]

I have a two speed speedometer adaptor for a big truck with two speed axle. Just wondering if anybody knows or has used one for changing the
speedometer for different size tires. Looks like it works by applying a 12 volt power and shifts. Don't know if adding power upshifts or downshifts
the speedometer. attaches to the back of speedometer. Does anyone know if these will even fit in our dashboards.

[chad67]

I had one of these on the back of the first F600 cluster I got. I just went out and tried it. It fits! As far as the shifting mechanism, I tried to hook power up to the gearbox while spinning it by hand, but I couldn't tell enough difference to give an answer on the down or upshift part of your question. I'll try to set up a more accurate test tomorrow. I wondered the same thing, except I was thinking about having 2 rear end pumkins-one for street, one for the strip and using the adapter to compensate.

[69Ford]

Thanks let me know how the test works out. I don't like to take out my restored bezel more than I have to.

[chad67]

The adapter reduces the speedometer cable speed when activated. The speedometer reading went from 70 mph to 55 with the adapter hooked to 12 volts. Of course these are aproximate readings.

[69Ford]

Thank you very much for checking