Anyone have any experience with one of these? There is the large head screwed onto the jack casing which seals the larger piston, then another smaller head screwed onto the larger piston that seals the smaller piston. It appears the heads are one piece and have to be removed to replace the packing. With both pistons fully retracted, there is no way to hold the larger piston to unscrew the smaller head. I'm afraid this jack is going to have to come out and go to a shop to replace the packings.

I "borrowed" this picture from Texacone