Abstract: A system for maintaining substantially uniform tension in an endless track for a track driven vehicle having a vehicle body and a suspension assembly and in which a tensioned endless track passes around end support and guide members, one of said end support and guide members being imparted vertical and some horizontal displacement relative to a rigid frame upon response of the suspension system to variations in loading and/or to terrain irregularities. The constant tension system provides a cam member having a cam surface in contact with the bottom surface of the top lay of the endless track, the cam member being supported by the suspension system and movable in correlation with movements of the suspension system so that differences in track length or track tension caused by movement of the suspension system will be compensated for and substantially uniform track tension will be maintained during travel of the suspension system.