TM 10-3930-669-34 CAUTION Keep  piston  straight  and  concentric  in  cylinder.    Do   not   allow   piston   to   become   wedged   in cylinder or damage to cylinder or piston may occur. (5) Remove base (3) from cylinder (1). (6) Remove piston (5) from cylinder (1). (7) Remove two screws (2) from base (3). (8) Remove backup ring (6) and preformed packing (7).         Discard     backup     ring     and     preformed packing. (9) Remove  wear  ring  (8)  from  piston  (5).    Discard wear ring. 15-47