TM 10-3930-659-34 4-70. FORK/BOOM CYLINDER REPAIR (Con’t). 17. Install key (5) and retaining ring (2) on rod (6). 18. Apply a coat of petrolatum to outer surface of piston (3). 19. Aline piston (3) with barrel (1), and push piston and guide (9) into barrel. 20. Apply a coat of lubricating oil to threads of four screws (7). 21. Hold barrel (1) securely, and install retainer (4) on barrel with four washers (8) and screws (7).  Torque screws to 660 lb.-ft.  (895 N-m). FOLLOW-ON TASKS: • Install fork/boom cylinder (see TM 10-3930-659-20). 4-293