Heavy Duty 3AX Container Chassis Tri-Axle Container Chassis. Heavy Duty Tri-Axle Chassis For 20 Ft. Containers. These tri-axle slider chassis are made to haul heavily loaded 20 ft. containers. The specialized heavy duty tri-axle container chassis was built for overweight 20 ft. containers. They have a more solid construction with deeper webbing and heavier I-beams...