Machine description: Mack EM6 6 Cylinder 672 cid Diesel 300 hp Engine, 2730 Engine hrs, Manual Transmission, 11R22.5, Camelback Spring Suspension, 189 in Wheelbase, PTO, Air Sliding 5th Wheel, Dual Fuel Tanks LOCATED-IN-F... more info about the 1985 Mack R686ST.