TM10-3930-660-34 16-18.   BOOM HOIST CYLINDERS - REPAIR (Cont’d) 2. RELIEVE PRESSURE IN CYLINDER BY SLOWLY REMOVING COUNTERBALANCE VALVE (1).  DRAIN RESIDUAL OIL THROUGH VALVE HOLES INTO A SUITABLE CONTAINER. 3. REMOVE BACKUP RINGS (2 AND 3), TWO BACKUP RINGS (4), AND THREE O-RINGS (5, 6 AND 7) FROM EACH COUNTERBALANCE VALVE (1).  DISCARD O-RINGS (5, 6 AND 7). 4. DISASSEMBLE CYLINDER PARTS (8-24). CAUTION Do not scratch or damage the wear surface of rod (8), piston or gland (9). Follow this precaution to prevent failure of the cylinder. a. Use a suitable tool to pull rod (8) out approximately 5 inches for removal of gland (9). b. Place a container under gland (9) to catch oil contained in cylinder. c. Use a spanner wrench to unscrew gland (9) from cylinder tube (10).  Pull gland (9) out of cylinder far enough to unseat O-ring (11).  Allow oil to drain into container. CAUTION Use care when removing rod (8) and piston assembly to prevent wear ring (12) damage.  Keep rod (8) in line with cylinder tube to prevent binding. d. Remove rod (8) and piston assembly from cylinder tube (10). e. Place rod (8) and piston assembly on suitable supports to prevent damage. 16-113