Abstract: Disclosed is a relay valve having a valve body with a longitudinal bore having axially spaced apart along its length and extending into the valve bore an inlet, and outlet, an exhaust, and a pilot inlet. A valve stem is slidingly mounted in the valve bore and is movable between a first position in which the inlet is in communication with the outlet and communication from the outlet to the exhaust is blocked, and a second position in which the outlet is in communication with the exhaust and communication from the inlet to the outlet is blocked. A piston is slidingly mounted in the valve bore and is movable with respect to the valve stem. The piston has a longitudinal piston bore and a piston spring is provided for urging the piston toward a closed end of the valve bore. A spool is connected to the stem and is slidingly positioned in the piston bore.