[weim55]

51-year-old truck and likely no one has ever had the hydraulic system completely apart and inspected everything. If you don’t know how old those wheel cylinders are replace or rebuild all of them. While you have the hardlines of the system open carefully check all the lines for free flow with compressed air, then flush the system completely with clean brake fluid. After 51 years many of these trucks have spent a lot of time sitting idle. Brake fluid can varnish and harden in the lines restricting or blocking flow.

Important stuff to check:

Are the brake shoes mounted backwards front to rear.

Is the brake clearance ( adjustment ) shoe to drum Correct?

Is the proportioning valve stuck One Direction allowing only one side of the system front or rear to actually function?

Are the parking brake cables to the rear functioning smoothly and correctly? ( you can never get a proper adjustment on the rear brakes if there is a problem with the cables )

With everything correct and ready to go properly bleed the master cylinder then properly bleed the rest of the system. The pedal should never go to the floor even under heavy stopping if everything is correct. While half ton drum brakes are not great, for anything under about 50 mph, they should stop the truck just fine. And yes, manual drum brakes do take a pretty heavy foot, though not excessive. With everything working properly, you should be able to Lock up all four brakes in a panic stop under 50 mph.t

Final words: Don’t try to do a piecemeal repair, this is one area where it’s important to just do the whole thing front to back one time correctly. If this is one of your first rodeo’s with drum brakes get a factory service manual to guide you properly.

Steve weim55 Colorado