Is it very common for the proptioning valve to go out? I have a 69 F-250 4x4 that sat and rusted for 10-15 years in coastal Alaska. I have replaced the brake shoes and drums in the front and the truck generally pulls to the right. Sometimes if I really stomp on the breaks it will go right then left. I plugged the rear brake lines to test it by welding up a brake fitting. The master cylinder is new and so are the wheel cylinders. I need help.

 

every drum brake i got goes right, then left real. bad in rain. i enjoy some rides i guess anythings possible thanks kevin

 

I have known of several trucks with drum brakes that after the fronts are replaced this problem showed up. My own included. A little hair raising indeed. I finally fixed mine by doing the adjusting as per the shop and owners manual. After initial manual adjustment, back up (vigorously if you can) then jam on the brakes. Do this as many times as necessary til the problem goes away. Worked for me.

This also needs to be done occasionally to keep the brakes adjusted. The little automatic adjusters in there are supposed to do this any time the brakes are applied in reverse, but I don't think it works as well as doing it on purpose, with vigor. It helps to do it on a steepish hill so the truck can coast backwards a little so you can hit the brakes repeatedly in a shorter space.

Also be sure the adjusting system on each wheel is in good shape with sharp edges where the stars meet the little lever they work together with. I lubed the threads inside and everything else with anti-sieze compound to be sure they stay free a good long time. The system does work as long as everything is free and in good condition. Somebody must have stayed up all night to figure that one out.