The Stovebolt Site Forums The Parking Lot Big Bolts 2 speed rear vacuum lines

A buddy of mine picked up a 48 chevy 2 ton "rw" chassis. Has two vacuum lines coming off of the rear not connected to anything. Anyone have an idea where they connect to?

Thanks

they connect to the two speed valve that is inside the frame rail just aft of the front axle.

There should be 2 steel lines running parallel,inside your driver's side frame rails. They "stop",just in front of your rear axle. From there,they connect to the "pancake",with rubber tubing,(Heavier walls,to resist collapse). Thanks,51 ashton,for the switch location. Hopefully vacuum line is still connected. If not,you'll have to install a line from your intake manifold,to the switch. One line ,on the switch,connects to the manifold. The other two fittings attach to the frame lines. Button down-"'Lo,button up,'Hi. If that's not the case,simply reverse the lines at the "pancake". Hope this helps.

On the 48 2 ton RW that I'm doing, the 2 speed switch that controlls the vacuum valve is mounted below the ignition switch. CCW is low, CW is high. There is a piano wire linkage that goes up to a 2 speed gearbox on the back of the speedometer to correct the reading when you shift ranges.

Good point,Jim! That switch is missing from my truck. The vacuum line has a pencil stuck in the end.That valve controls the speedo,and not the 2-speed. It keeps them "in sync". I thought that the line was for the heater,somehow,until a similar topic popped-up a while ago.

The switch handle is on a rod that goes through the firewall, a linkage connects to the vacuum valve on the frame. When the handle is turned the valve moves up and down and switches the vacuum and the speedo gears change at the same time. A large vacuum line runs from the manifold to a junction on the firewall that supplies vacuum to the brake booster and rear axle valve. All of these lines are larger than a pencil. There is a smaller vacuum line that comes into the cab to rum the windshield wipers.

I stand corrected! Yea,NOW I remember the "bicycle bell" style switch used on the A.D.'s. My T.F.'55 has a different set-up entirely. I have electric wipers,so I'm sure my line, "flopping in the breeze",attaches to the speedo,when I can locate the part. Sorry for the mistake. The origional location for the 2-speed switch,(on my truck),was mounted on the tranny.The cable is mounted on the shift rod.