Abstract: A stabilizing system includes multi-stage locking pins connected to a trailer fifth-wheel plate and a tractor fifth wheel plate. Each multi-stage locking pin includes contiguous members that have altering diameters. A mechanism is included for telescopically displacing the contiguous members such that the contiguous members become aligned within a pair of apertures in the fifth-wheel plate assembly. The apertures are movable about the multi-stage locking pins. A speed detecting mechanism cooperates with the displacing mechanism for automatically adjusting the tolerance angle. The speed detecting mechanism emits intermittent notification signals to the displacing mechanism during transit. The tolerance angle has an inverse relationship to the tractor speed. A lower one of the contiguous members has a diameter generally equal to a diameter of the apertures respectively and a top one of the contiguous members has a diameter less than the aperture diameters.