The Stovebolt Site Forums The Parking Lot Big Bolts 2 speed shift selector

the dash mounted 2 speed shifter in my 46 creates a vac leak
i tried to fix it but the guts are worn out. where can i find a new one. or what can i replace it with. philip

The 2 speed vacuum shift became obsolete in about 1954 and parts were not available very long after that. I remember some being repaired in the 60's by using an air valve. Spring pressure holds the axle and the speedo adapter in the low range. When vacuum is applied, it pulls the axle into high range. The turning on and of of vacuum can be accomplished with with an air valve. I have one that the speedo adapter leaks vacuum. I have been thinking about using an adapter from an electric shift to shift the speedo, but I haven't really got into it yet.

Not an original-equipment fix, but how about valving the vacuum with a fuel tank selector valve? It could be dash-mounted and plumbed to apply or remove the vacuum from the axle-mounted shift system. It might be necessary to create a small bleeder orfice somewhere to prevent vacuum from being trapped in a line when it's supposed to dissipate.
Jerry

Had asimilar issue with some of the bits & pieces for my beastie. Took some time but I found nearly identical new parts that fit th bill.
Pull the valve offand go see your local hardware stores and places like Napa, you may find something similar that can be adapted to fit and still look like the original.

All three of the trucks I have with two speed rears are vacuum shift but they are not on the dash the valves are under the truck next to the transmission and controlled with a knob and cable on the shifter. Both the 56 and the 57 shift the speedometer with vacuum the 64 shifts the speedometer electrically so its knob and cable also has a switch built in for the speedometer. and my friend has a 72 that has the same rear end as my three trucks so the vacuum shifted rears were around till at least 72.
I haven’t seen the internals of the dash mounted valve but I bet you can rebuild it with standard o-rings and seals try and industrial outlet like Seal Source some of the bearing outlets also have a good selection of seals and o-rings. If you have a local industrial hydraulics shop you may check with them if they can’t help they should be able to direct you to someone who can.

GMC books from 55 and later call for an electric two speed, both on Eaton and their corporate 2 speed. An electric shifter might fit on the housing where the vacuum shifter was. If not, call these guys. They have a lot of odd seals etc. and are very helpful. http://www.baumhydraulics.com/home.php

I have a 68 Chev C50 & it has a vacuum shift.
You should be easey to get it to work.