Abstract: A load hauling trailer assembly adapted for on and off road use includes a towable mobile chassis, a storage container body mounted on the mobile chassis and having an open top, a top cover having an outer side and being mountable on the storage container body and movable between opened and closed positions relative to the open top of the storage container body, and a carrier rack mounted on the outer side of the top cover and adapted to carry gear thereon when the top cover is mounted on the storage container body and moved to the closed position. The mobile chassis includes a frame structure, a pair of wheel subassemblies, and suspension and frame structure height adjustment subassemblies mounted to and extending transversely of the frame structure and mounting the wheel subassemblies to the frame structure.