TM 9-2320-209-20-3-3 b. Adjustment. NOTE This task is the same for the horizontal and vertical leveling worm drive chains. This task is shown for the horizontal leveling worm drive chain. 1. 2. 3. 4. Check free play by putting 12-inch ruler on chain (1) as shown. Firmly push down on chain with zero end of 6-inch ruler halfway between sprockets (2). Read free play on 6-inch ruler at bottom edge of 12-inch ruler. Using 3/4-inch wrenches, loosen capscrew (3) and nut (4). Using 1 1/8-inch wrench and 2-inch wrench, hold chain tightening shaft (5) and turn eccentric bushing (6) until free play is 1/2 inch on chains (1 and 7). Using 3/4-inch wrenches, tighten capscrew (3) and nut (4). NOTE Follow-on Maintenance Action Required: Put on leveling worm drive chain cover. Refer to para 18-78 for horizontal leveling worm drive chain cover replacement. Refer to para 18-79 for vertical leveling worm drive chain cover replacement. END OF TASK 18-435