Machine description: Mack 6 Cylinder 11.0 L Ultra Low Sulfur Diesel 235 hp Engine, 1987 US EPA Label, 2702 Engine hrs, Mack 5-Speed Manual Transmission, 11R24.5, Camelback Spring Suspension, 230 in Wheelbase, 22 ft x 96 i... more info about the 1981 Mack R686ST.