Used Mack GU713 Tri-axle Dump Truck for sale. Features: 20,000 lb. non-steerable lift axle, Heated Body, Steel Beau-Roc Dump Body, Power Locks, and more. Visit Liberty Kenworth and Coopersburg Kenworth to see our HUGE inventory of new and new and used dump trucks, daycabs, sleepers, trailers, and more.