A vehicle air dryer comprising: a dryer cylinder for drying compressed air passing therethrough, an exhaust assembly for providing an additional air outlet, a backflow assembly for providing a backflow air passage, an air pressure governor assembly for maintaining air pressure inside the vehicle air dryer, an one way check valve for providing one way air passage for dried compressed air and preventing air leakage, and a dryer valve body having an air inlet, an air inlet chamber, an air outlet, a slanting air passage leading to the air outlet, a first opening for installing the exhaust assembly, an opposite, second opening for threadingly attaching the dryer cylinder, a third opening, substantially perpendicular to the second opening, for mounting the backflow assembly, and a fourth opening, substantially parallel to the third opening, for receiving the air pressure governor assembly.