I think I payed around $70 for a brand new valve off ebay less than a year ago. I don't remember the name of the co. that makes them though, I threw the box out.

 

Thankyou for the compliment, I'm more than happy to help if I can.
However, I think you misunderstood what I was saying about the prop. valve. On our trucks (all vehicles actually) there are two SEPARATE brake systems, front and rear (some cars, GM X bodies for example, used diagonal braking, not smart).
Both of the systems are INDEPENDENT of each other. If you break a line, blow a wheel cylinder or whatever you will lose all of the fluid in that half of the system. There is nothing to stop the fluid loss. The prop valve doesn't function as a check valve.
What the valve does do is function as a sensor. The brake failure switch is mounted between the two systems. When things are functioning normally there is pressure on both sides of the valve keeping the valve spool centered. If you have a system failure and lose pressure in one of the systems you will now have pressure on one side of the spool only. This will push the spool to the low pressure side and trip the switch. This will cause the brake failure light to come on and stay on untill the system is restored and pressure is on both side of the spool.
I just wanted to clear up any mis-understanding.

 

TMI, good luck let me know how it turns out.

 

When my proportioning valve went out last year my research led me here for some answers (I love this place). I ended up going to a junkyard, cost me $25 and I reused my old switch (still have the other as a spare). This is by far the best forum that I have found for good answers to questions on Ford trucks. And the people on here are pretty good, as in not flaming *********s. Good luck with your project, and post pictures 'cause we all like pictures on here.

 

Hi

that page from the manual will not download.

could yous end it to klein.gerald@gmail.com

please and thank you

G