The Stovebolt Site Forums The Parking Lot Big Bolts vacuum line on speedometer and other things

1. So I pulled the dash today of my '59 viking60 to replace the nonfunctional lights and the wiper switch. As I got it out, I was noticing and wondering what that thing was right about where the speedo cable attaches. I realized it was a diaphragm and then I saw the unhooked hose. I hooked it up, but have not driven it yet and can't figure out what it is for and have not yet found any info about it on the net or here. I need someone to enlighten me on what that is for.

2. It appears that this old girl has a single speed wiper motor. I just thought the switch was bad and only hi worked, cause when you turn them off they seem to park at low speed. I only have two wires running from motor to switch. Is this correct that they have single speed motors?

thanks for all the incredible information y'all

welcome to the site!
1. That vacuum diaphragm controls a 2-speed gear box for your speedo so that when you shift the 2 speed rear into low, your speedo shifts into low as well and still shows the correct speed. necessary? no, always accurate? no. available, no! lol. in my experience, I use low on the rear when towing and pulling up a hill, with my foot in it, that means low or no vacuum which means, the speedo stays in high anyway. It is cool to have it working though!,

2. there are only 2 wires going from the motor to the switch, but it is a 2 speed. The switch supplies ground, + is supplied by a wire from the key switch (that is why the wipers stop as soon as you turn off the key, and do not return to park. The park function has a separate ground, which may be a bit dirty and the reason the park function is real slow. Mine is as well, most of the time!

Stephen5971 My 51 6400 has a wire link that shifts that speedometer box from the 2 speed control,so very glad it works. Is pretty accurate and smooth after72 years. Whole truck is pretty good !