I am going to change my master cylinder/booster next weekend but I want to make sure that is the entire problem,
so I turn to the people who know
The problems are:
sometimes rock solid pedal after the truck sits for a while, slowly goes down
and sometimes the opposite, soft pedal
also the obvious persistent leaks between the booster and master, but another problem that leads me to believe there is something else going on is when braking on ice the front tires lock up while the rear tires just keep spinning, until the pedal is pressed much more firmly, maybe the proportionate valve? If this valve is a problem, is it in the master/booster assembly, or is it the long rectangle block on the right side of the master/booster?

Thanks

 

Sounds reasonable, but make sure that the rears are adjusted correctly, very important...Mark

 

if everything isn't rusty its easy to adjust the rears with a screw driver... that being said its a night and day difference when you re-adjust the rear shoes.

 

I have adjusted the rear shoes for the park brake, same adjustment?

 

If it was from the back side of the drum, a starwheel you spin with something similar to a screw driver. i adjust mine until it rubs ever so slightly. and i think it re-adjusts every time you apply the parking brake(or it should)