Unscrew both nuts on the rod until they are flush with the end of the stud (make sure to do both so there is room for the cap to separate). Then use some sort of a flat bar (socket extension will work) and place it on the nut/stud end. Tap the other end of the bar lightly with a hammer (Do NOT hit the nut/stud itself with the hammer. Although not likely to mushroom since the nut is there, it still risks some potential problems). This will take the cap right off without damaging anything.