1988 GMC 1500 Brakes

[drumsdaddy]

New guy to the forum.

I have pre-owned '88 GMC 1500 and I have a brake problem. It started out as a "brake light" that stayed on. Further investigation of the system and I found that the entire brake system needed replacement. I replaced the following:
New rear shoes, new cylinders, new brake hardware, turned rotors and drums, new brake hoses, replaced (2) rebuilt master cylinders, replaced a single diaphragm vacuum booster with a dual diaphragm booster (rebuilt), replaced the molded vacuum booster hose. I did not replace the front calipers. I checked them and they are working correctly. My results of all this work leaves me with a hard brake pedal that won't stop this sled. Before all of this work I had a soft pedal that wouldn't stop this sled. The only thing left besides the front calipers is the proportioning valve. I have one ordered so I'm hoping this is the problem. No, the "pin" did not extend out to be pushed back in to bleed the brakes as it explains in the shop manual. I took the old valve apart and found that the valve inside the body was stuck. It took some muscle to remove the valve. Shouldn't have to "muscle" a valve as small as that! I did notice when I was bleeding the system that there was a small amount of leakage at the ends of the valve.

Yes, I have a power bleeder and bled the lines numerous times.

I did remove the RWAL part of this system and tied the lines to the proportioning valve in the correct way. I am not a fan of electronic brakes on any vehicle.

So that's about the size of it. Any and all help would be much appreciated!

Thanks!

Drumsdaddy