WHOA....those are brakes

[Longhorn Man]

You may need to back off the adjustment on the pushrod a bit.
When the truck is cooled down... like a few hrs with no driving, depress the pedal lightly with your hand. You are looking for some freeplay. I'm thinking there's supposed to be something like 1/4 to 1/2 inch freeplay... something like that.

The fluid expands a little with heat, and since drums retain heat, the fluid heats up. Havinf drums up front increases the heat by more than 100% since they do 75% of the work. This increases the amount of slack, or room needed to expand.

When I replaced the master cylinder on my first truck(70 CST/20 Longhorn) I over adjusted that push rod, and once i got on the freeway I noticed it was suffering from LOA (lack of @ss). Once I got on the next off ramp, it was draggin even worse, and then I smelled the rear brakes. They were slightly applied becouse the fluid had expanded. I popped the master off, turned on the rod end about 1/2 turn, bolted it back up...tail lights and tire smoke.