I plan on fixing the two speed rear soon as the worn 292 doesn't like to move the truck with the dump bed loaded.
I removed my instrument cluster and there isn't a vacuum switch on the speedometer. I looked at another '64 C60 with two speed rear today and it has the same aluminum device bolted to the inside fire wall behind the pedals and no vacuum switch on the rear of the speedometer. The funny thing is, there was not a wire hooked to this one either! This one also had only a cable with a knob going from the vacuum switch up to the transmission shifter, no electric switch to operate the speedometer device could be seen.
Did GM make shop manuals for 60-66 Medium Duty trucks? All I have found are for the Light Duty trucks.
