rear brake valve

[board350]

here is another question for all you wiser than I toy folks. The rear brakes on my 84 just quit working the other day and i am confused as to why. The weird thing is that i am getting fluid back there but not expanding the wheel cylinders. I know this when I was bleeding them after pulling my axle apart. I am guessing it is the proportioning valve malfunctioning. Could someone explain to me how that thing works and what might be wrong? Thanks

[4rnr4evr]

ok this is how i understand it the lever that runs from the valve to the rear axle is a load sensing rod when youre truck is loaded the rod swings upward allowing more preasure to get to the rear brakes.or act as a antilock brakes when youre hitting the brakes real hard youre truck dives in the front and the rear cums up lighting the load in the rear tires the rod swings down and reduses the preasure to the rears. keeping the rears from locking up........now what i did was elimanate the rod that runs from the valve to the rear axle. cut the rod about 6" long sticking out from the proportioning valve.weld a flat tab on top of youre frame directly above the 6" rod .drill a 3/8" hole in it then weld some all thread to the 6" rod so it runs up through the 3/8" hole in the tab. put a nut on both sides of the allthread so you can adjust it up and down to adjust the preasuere to the rear brakes.. it works perfect on my truck and the dont lock up on gravel either!

[Possum]

Would you need to drop that rod down before you bleed your brakes to keep the pressire right....

[4rnr4evr]

if you dropped the rod down wouldnt the valve think the truck is under hard brakeing? and decrees the fluid? i would say you would lift it up so the valve thinks the truck is loaded letting the full amount of fluid to the rear brakes?

[board350]

I think what is ment is to adjust it so there is not too little or too much pressure. All the way up would lock up the rears before the front.

I am really befuttled by the dual lines running to the thing. What the heck is all that about? A pressure return line or something?

[robrocketanski]

i thought the same thing while playing with mine and determined it is pointless to have two lines (i am sure there is a reason but....) the two lines come from seperate parts of the master, primary and secondary, so that destroys the purpose of that (usually they are crossed or split front and rear) and if it goes to one line to get to the rear axle then it is cancelled out again. hydrualic pressure cant stay divided if it all goes to one line.

i think i set up the truck i had to run one port of the master to the rear w/ one line and two lines to the front off of the other port.

[pipefitter]

The valve is for adjusting the brake presure when you carry weight in the bed . You can put a adjustable valve in or put a new stock one on and just cut the rod off . If you do that the brake presure will be like you are running without weight in the bed .