The Power Assist type uses a special Drag Link with an integral hydraulic control valve that controls a hydraulic cylinder that's connected on one end to the frame/crossmember and to the tie rod with the other end. As the drag link is pushed or pulled by the steering pitman arm the cylinder assists the driver in pushing or pulling the tie rod. This system was used in everything in the late 50's and 60's. and does a decent job. That said, it doesn't compare to todays power rack and pinion.
Mike B
