TM10-3930-660-20 18-24. BOOM  EXTEND  AND  RETRACT CHAINS - INSPECT/ADJUST (Cont’d) 4. 5. 6. 7. LOOSEN OR TIGHTEN ADJUSTING LOCKNUT (2) UNTIL CHAIN IS WITHIN SPECIFICATIONS. a. b. c. Loosen jamnut (3). Loosen or tighten adjusting locknut (2) until chain sag (1) is within specifications. Tighten jamnut (3). RETRACT AND EXTEND BOOM SEVERAL TIMES. RECHECK CHAIN SAG (1). a. Chain sag (1) should be approximately 3-1/4 to 3-1/2 inches (83 to 89 mm) from top of chain to bottom of boom. CHECK TENSION OF HYDRAULIC HOSES AND BOOM ELECTRICAL CABLE, PARA. 18-25. 18-95