The Stovebolt Site Forums The Parking Lot Big Bolts Todays Mystery Part - a Vacuum Valve

I pulled the engine from my 58 Viking, got to looking at the vacuum system, and I realized the cover to the vacuum valve that shifts my rear end is missing. I am hoping to replace the cover, but I can't find what part number this is. Anyone here have an idea? Or at least a flow diagram so I can use a different valve?

Pics of the valve.

https://drive.google.com/open?id=0B6Aw4aYru4MTS3ZyckZnSnlfS2c

The rear end is a GM 2 speed, I guess the valve is original.

I believe it does not have a cover that side mounts directly to the frame so that's how it get covered. That's how mine is anyways.

Odd, guess I will have to build a bracket. Does yours use a gasket, or is it open to the elements?

Your missing the plate steel mounting bracket (mounting bracket and side cover all in one). It is shaped kind of like the State of Texas with a slight bend in the middle and 4-holes in it. Two holes are used to screw the selector switch to the plate and two are used to mount it to the transmission using longer top cover bolts.

Hopefully you have this funny looking piece in your junk parts box and just didn't know what it was...

Mike B

Sorry Mike, no luck. The plate must have been removed by the mechanic when the new engine got shoehorned in. Can I get a picture of this plate? I will just have to overbuild a new one.

Before you get in a hurry to get the cover have you confirmed the selector switch even works? Just cut temporary cover out of a cerial box and tape it in place and see if it works.

There are 4 ports:

Main Vacuum from manifold.

Hi range to rear.

Lo range to rear.

Small line to speedometer cable reduction unit mounted on the back of the speedometer.

I'll see if I have a bracket to take a picture of when I get home.

Mike B

The switch works, I can tell when the rear shifts, but it is difficult to move the knob, and I believe the dust is a major contributor. The valve seems to hold its own on just the hoses, but I would feel safer with a steel bracket, and now is the time to put it in.

Heere's a couple pictures of the bracket you need...should be easy to make.

http://s160.photobucket.com/user/st...uum%20switch%201.jpg.html?sort=9&o=1

How did you test your switch without the cover?

Mike B

I have driven the truck, and when I pull the knob out, the rear end shifts hi, and pushing it in shifts low, along with a corresponding change in the speedometer. The valve shifts, but it relies on the rigidity of the hoses to keep it from moving, an obvious failure point I would like to remove.

The plate is an oddity, perhaps I'll be better served fastening it to the cab, instead of the transmission?

Place an ad in the wanted section, I bet someone can help with a used bracket.

Mike B

Can someone link me a picture I can download? I doubt I can describe it accurately enough for the wanted section.

Casey,

Here's the way I'd write it up (feel free to use this or edit it to your liking), but I think anyone that has this part will know what you need with this discription.

"Wanted, 55-59 2-speed rear vacuum selector switch mounting bracket/cover. The bracket mounts to the top of the SM-420 transmission and holds the cable actuated switch in place."

Good Luck!

Mike B

Could he also add a link to this thread? Or isn't that allowed in the swap meet?

Mike, I couldn't think of any way to write that better, Thank you for the help.

There's a guy in Oregon that sells mostly '55-'59 T.F./ Blue Chip Parts. He Has a lot of 2-tons. He has a Site on "Youtube",called "Classic Truck Rescue". I Know He Has What you're looking For.