It has to be an oil flow problem from the pedal, I would place the truck in neutral, remove the lines at the pedal and crank or momentary start to c where the oil enters the pedal. Then put that hose back on and check flow exiting pedal in both forward and reverse. It'll tell u if the pedal is good
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.