TM 10-3930-659-20 15-1. ON-BOARD CRANE MAINTENANCE (Con't). 6. Install shaft collar (14) on mast (16) with pin (15) and spring lockpin (13). 7. Install rear groove pulley (18) on boom (6) with pin (5) and new cotter pin (7). 8. Install pin (17) and spring lockpin (8) on mast (16) and boom (6). 9. Install two spacers (10) and front groove pulley (11) on boom (6) with pin (12) and new cotter pin (9). TA706766 15-8