Garage door opener makes loud banging, grinding, or clunking noises during operation.

Safety first: Disconnect power before tightening hardware or working near moving parts.

• Inspect chain/belt tension: For chain drives, adjust tension so there is about 1/4 inch sag at the midpoint. For belt drives, follow Craftsman specs for slight deflection.
• Check sprocket and idler: Look at the top sprocket and any idler pulleys for wobble, missing teeth, or metal shavings. Replace worn components.
• Secure rail and header bracket: Tighten all bolts connecting the rail to the opener head and the header bracket above the door. Loose brackets can cause banging.
• Inspect trolley: Check the Craftsman trolley for cracks or excessive play on the rail. Replace if worn.
• Lubricate moving parts: Apply garage door lubricant to the chain (if recommended), hinges, and rollers. Do not over-lubricate the rail.