Chamberlain LiftMaster PREMIUM Series Manual page 5

Assembly
2
Tighten the Chain
2.1
Loosen the inner nut and lock washer on the trolley threaded shaft.
2.2
Tighten the outer nut until the chain is a 1/2 inch above the base of the rail at the midpoint of
the rail.
2.3
Re-tighten the inner nut.
Slack in the chain is normal when the door is closed. No readjustment is necessary.
NOTE: Sprocket noise can result if the chain is too loose. During future maintenance, ALWAYS pull
the emergency release handle to disconnect the trolley before adjusting the chain.
5
1/2"