I'm going through all the mechanicals on the 2nd series '55 6400 I bought a couple years ago and the vacuum switch on the shifter (push/pull knob) is not working in a responsible manner! The diaphragm has been rebuilt on the diff and seems to work properly. I isolated the vacuum lines from the brake vacuum unit. The switch seems to work sometimes, not others. Can it be torn down, cleaned, and repaired? Is there a website that discusses this? Or is there a known good (easy) electrical replacement for it? I've searched about everywhere and am not finding info on the vacuum switch.
