US Patent 7111862 Unitized fifth wheel and rear axle suspension

A modular suspension system for short distance repositioning tractors, often referenced as terminal tractors, isolating the shock and impact of a retractable fifth wheel and rear axle from the frame of the terminal tractor by the arrangement of a rear axle and fifth wheel boom having lift cylinders between them and joining the rear axle, a lift arm assembly and a trailing arm assembly as a singular modular unit, isolated from the frame of the terminal tractor by elastomeric bushings at a forward location and pivot point on the terminal tractor frame, with a secondary suspension located at the rear of the singular modular unit.