VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Vacuum Shift Check Valve

Is the device mounted to the frame rail, with the vacuum line leading to it, from the vacuum cylinder a check valve?

The vacuum shift unit does not have a check valve. The main unit is attached to the transmission. There is a vacuum source hose from the intake manifold that attaches to a pipe that is further attached to the vacuum unit. There is another hose that goes to a filter unit on the frame rail.

Although it works wonderfully right now, would said filter cause poor operation if it were to be plugged? What is the filter element itself? How do you clean it?

To be honest I have never tried to open the filter unit to see what is inside. I think the filter keeps the large particles from getting into the vacuum cylinder. If plugged, it would likely affect the operation of the shifter.

What years did Chevy us this vacuum shift? I'd like to know a little more about them.
I was a parts man for Chevrolet back in the late 50's and early 60's until I went in the service in '64. I realize by the late 50's these would have been considered antiques but in the five years that I worked for Chevy I never saw one nor was I even aware of them.
Denny Graham
Sandwich, IL

Denny I belive 1948 was the last year for the vacuum assist. I drove a '41 with it and it worked great.
Cleon

The Vacuum shift was first placed on the 1939 and continued to 1948. 1939 was by itself and the 40-48 are the same.

Thanks guys, I downloaded the transmission section for the 40's thanks to Keith H. and I'll study the setup. Been thinking about something in the autocar class from the late 30's or 40's for my next project I'm just doing some early ground work.
Denny Graham
Sandwich, IL

Stylemaster
While I have no knowledge of the vacuum shift system I tend to agree with Ray in that if the filter was plugged it would affect the operation as it would require outside air pressure to work properly.
Tony

The vacuum shaft canister on the 1939-1948 has a round filter unit bolted to the inside of the driver's side frame by 2 small tapped screws. When removed from the frame, there is a thin round plate inside this unit which has multiple air holes drilled in it. Inside the filter unit itself is a wire mesh similar to the air cleaner wire mesh. You can take this unit apart, clean it with kerosene and reassemble it. Sandblast and paint if it is rusty. I would put no oil or anything on the wire mesh inside as that will just attract dust and dirt to stick to it. make sure the rubber hose from this unit to the vacuum shift canister is clean on the inside of the rubber hose while you have this unit out of the car.

dtm