Abstract: A fifth wheel is illustrated having laterally extending wedge-shaped integral continuations of the fifth wheel for engaging a stop carried beneath the bottom surface of the trailer to limit angular movement between the tractor and trailer. Grease fittings and passageways are provided for greasing the upper surfaces of the wedge-shaped projections so as to facilitate their support of the trailer during turning. The connecting and operating of the tractor-trailer rig is facilitated by the application of grease to these upper surfaces which due to their extreme lateral disposition, engage the lower surface of the trailer magnifying the need for the application of grease.

Abstract: A tractor-trailer coupling including a fifth wheel on the tractor pivotally receiving a king pin on the trailer. Cooperable structure is provided between the tractor and trailer which is operable during highway driving to prevent the tractor and trailer from pivoting relative to one another to a sufficient extent to cause vehicle jackknifing. This cooperable structure can be rendered inoperative to allow greater pivotal movement between the tractor and trailer in tight maneuvering conditions. In addition, cooperable stops on the tractor and trailer prevent the tractor and trailer from pivoting so far that their sides can engage and cause damage to the vehicle when the jackknife preventing structure is inoperative. The jackknife preventing structure is rendered operative and inoperative from within the tractor cab.