Brake Proportion Valve, and slow reation from the brakes.

Like in the photo, there is a the main supply. Follow the red line and you will find the proportioning valve.

 

I thought it was all in the front valve. Guess I missed something? Either way, interested in findings. I wasn’t able to find the explanation of how the 50% front thing works, or if and when it was discontinued. My understanding is it was discontinued with abs. The purpose being to keep steers from locking up. Very important in snow and ice. I once slammed on the brakes, and spun like a top about a dozen times bobtailing in a old Daycab, right out into a roadway. Lucky no traffic. Hair raising learning experience.

 

The valve gives full power to the steers and 50% to the rear.

This guy is annoying to listen to but here is a video of it. A couple i had, had just the proportioning valve on the treadle.

 

Normal treadle valve. Proportioning valve is only for rear axle brakes, cuts air pressure to them by 50%. Can't tell from the picture, does your rear service valve have a line/hooked direct to an air tank? That can't be seen in the picture? If so then that is the proportioning valve. If it is then the red lines should only have air to it when the trailer brakes are released, that needs to be constant to by pass it.

Or come through Green Bay and i'll fix it. LOL

 

I blew up the picture and put on my glasses. Unhook the red line, not air should come out until you release the trailer brakes. If so, cap the line and run another full pressure line to that port and you're done. Has to be tank pressure all the time.

 

So after owning the truck and working on it for a few months I figured out my problem. My truck doesn’t have a proportioning valve. My issue was the brake valve plunger on the firewall. The gasket was gone and water got inside and the plunger was basically seized. I had no brakes until the rod would hit the plunger where it was seized which was far down and then it moved just a bit. Replaced the valve, plunger and housing along with the gasket and have excellent brakes now.