The Stovebolt Site Forums The Parking Lot Big Bolts 1946 2 speed

Finally got the vacuum lines hooked up on my truck. My truck has a switch that is mounted in the dash. I have one line going from the intake to the switch, then there is two lines going out of the switch, both of these lines I plumbed straight to the 2 nipples on the rear end. When I flip the switch one way, I have some vacuum on one line at the rear end, when I flip it the other way I have nothing in either line at the rear end. I plumbed the whole system with 3/8 hose. I took the truck for a test drive and it will not shift. I dont know much about these systems so if anyone can tell me what I did wrong or what I can try to get it to work it would be much appreciated.

Hy jdchevy, welcome, if I'm remembering correctly a spring pushes the shifter into low range when there is no vacuum. Most of the dash controls I have seen say "Park In Low" on them, because when the vacuum is gone the spring will try to push it into low range anyway. You should have check valves in your system, when you open the throttle when driving along your engine vacuum will drop and that may allow the vacuum in the two speed shift diaphragm to drop to the point that the spring will push it out of high range. You should test the integrity of the diaphragm before you go too far trying to get the shift system to function, hope that helps