tractor and bulldozer to avoid the necessity for multiple braces extending angularly between the push arms 16 and the back of the blade such as the braces disclosed in u s pat no 3 049 820 assigned to the assignee of this application the single rigid link is entirely located between the forward end of the tractor and the blade and extends transversely of the tractor in substantial parallel relationship with the blade the first end of the link is pivotally connected to a bracket 28 on one push arm by a ball and socket joint 29 and the second end is pivoted to a bracket 30 depending from main tractor frame members 32 by a ball and socket joint 33 since connection 29 on one push arm is located at a lateral end of the bulldozer on the first side of the tractor which is remote from connection 33 disposed on the second side of the tractor the arcuate travel of the link at joint 29 is very small thus raising and lowering of the blade by actuators 22 imparts only an imperceptible motion thereto with this construction link 26 acts as a rigid brace between the main frame and the bulldozer blade which prevents an appreciable sidewise motion of the blade referring to fig3 a tractor identical with that shown in fig1 is illustrated with the engine and engine housing removed a c frame auxiliary frame 35 has its free ends connected by ball and socket joints 37 to.