To use the Grainger valve, where do you connect it to lock all four wheels? Wouldn't you need 2 valves because no one brake line ever feeds all 4 wheels, right? Also, you'd have to run some brake lines up into the cab so you could get to the valve while your foot is on the pedal. Is this right, how did some of you guys do this mod, I'd like to beef up my parking brake capacity.
