Machine description: Mack EM7 6 Cylinder Diesel 300 hp Engine, 1990 US EPA Label, Positive Air Shutoff, 4421 Engine hrs, Engine Brake, 5600 kg Front Axle, 9100 kg Rears, 315/80R22.5, Spring Suspension, 218 in Wheelbase, P... more info about the 1991 Mack RD690P.