The Stovebolt Site Forums The Parking Lot Big Bolts Bendix 2 speed vacuum shift

Are there rebuild kits or replacements for the 2 speed vacuum shift module? Not the actuator that bolts to the axle but the module with the push/pull cable. The rubber and gaskets are rotted out on mine. What have others done to repair or replace? 1957 6400

I replaced my two speed of low and lower gears with a modern single speed for highway driving!

Ed

I had a cracked housing on my shifter when I started work on my 9600/350. I was able to find a NOS housing on Ebay.

The rubber pucks seemed to seal just fine for me. I dabbed RTV around the gasket surfaces when I put it back together to make it airtight.

For your dry-rotted rubber, you could try getting someone with a 3D printer to make a couple of replacements out of TPU filament. I don't know how well it will hold up to exposure to petroleum, but it is worth a try. I am trying it out on the slide valve for a Trico wiper motor I cleaned up.

The final option is to find a electric shifter off of a newer C50/60/65/70. The axles between the AD and the 1960s models didn't seem to change much. The vacuum shift option did go into the sixties as well, so you might be able to find shift valves on those models as well.

One other alternative would be to look into pneumatic solenoid valves. You would need to look for a "reversing valve" to get the flip-flop action of the original shifting valve.(See next post for a better search term and explanation - 5/2 valve) A lot of those valves use 24v coils as that is what a lot of industrial PLC controls use, but 12v should exist, and the coil section itself is pretty modular.

McMaster and Automation Direct are a couple of places to check for those valves.

One thing to research if you are thinking of an aftermarket valve, the vacuum valve for my '57 has 4 ports, vacuum "in" from the engine, vacuum "out" for low range, vacuum "out" for high range, and exhaust "out" to the exhaust side of the system. The valve has to be able to shift the vacuum to the actuator in both positions but also has to be able to exhaust the circuit that is being de-energized.

I did some more research, and a "5/2 pneumatic valve" would do the trick. Those are designed for double-acting cyilinders, which the vacuum actuator on the two-speed axle would act like, and then have control over the exhaust. You would have the vacuum supply line go into the main supply port, and then tie the two exhaust ports together to go to the open-air vent. For the speedometer range box, you will have to tee off of the vacuum line that actuated the appropriate range on the axle.

I have attached a couple of pictures - one shows an example of a 5/2 valve, the other shows a annotated engineer symbol with the letters matching the ports seen on the example to demostrate how the valve would be hooked up. These valves are quite inexpensive - amazon.ca shows one for twenty bucks for a 12V version of the valve with 1/4npt ports.

Non-electric versions can also be found, but would require some creativity if you want it to be cable actuated like the original.

That valve might do the trick, then a push-pull switch could be mounted on the tranny shift lever where it's supposed to be so the truck can be split-shifted with ease. Edit: I had this thread confused with the other 2 speed thread, looks like your 2 speed selector is already on the shifter.

Thanks. Good ideas!!!