Brake pedal can be pushed nearly completely down to the floor when standing

[[__--MUD--__]]

that isn't right... that noise you are hearing is your powersteering pump getting dragged down or the belt slipping.

if your not aware, your brakes are a hydroboost system which is run off your powersteering pump.

My service manuals are at the shop, but i think w/ the truck off- pump the brakes 4 times hard, hold the pedal down on the last pump and start the truck. I believe it should pump up, or feel the pedal push back on you.

My rigs been torn apart for 8 months under a massive rebuild otherwise I'd go out and confirm that for you.