Thanks 69Cuda, Rich and Paul for your images and observations. It is as I suspected, fill the cylinder. Does anyone have a cutaway view of one of these cylinders? I would sure like to understand how they work. I am guessing that one larger cylinder is around a smaller pressure cylinder with the pump being lower and has a supply from the outer cylinder, then through the pump and pressurizes the pressure cylinder and pushes the ram. Of course the flow is regulated VIA the control lever in the cab. Any other thoughts?
Al
PS: I am not sure I can worm under my truck with the bed down and fill the cylinder. I will study one more time before I bring in the front end loader to lift the bed.
Alan