TM 9-2320-209-20-3-3 18-80. LEVELING WORM DRIVE TOOLS : 2-inch wrench 3/4-inch wrench 12-inch ruler SUPPLIES : None PERSONNEL: One CHAIN ADJUSTMENT (TRUCK M764). 6-inch ruler 1 1/8-inch wrench EQUIPMENT CONDITION : Truck parked, engine off, handbrake set. a. Preliminary Procedure. Take off leveling worm drive chain cover. Refer to para 18-78 for horizontal leveling worm drive chain cover removal. Refer to para 18-79 for vertical leveling worm drive chain cover removal. 18-434