A track frame or undercarriage is made to support a rubber track on suitable guide rollers. A tensioning roller is provided as one of the guide rollers on the interior of the track and is mounted on a pivoting bracket. The pivoting bracket moves the tensioning roller to a working position for creating tension in the track. An actuator provides a known force on the pivoting bracket to move the tensioning roller to its working position, using a controlled pressure applied to the actuator. Drive sprockets for the track are mounted onto a drive case that is mounted to the frame through pivoting linkages such that the drive case and the drive sprocket can be held in a working position and retracted away from the track. The position of the tensioning roller is maintained within set limits of retractions during use, by providing a stop to limit the amount that the tensioning roller can retract.