Diagnosis
That's the sound of the motor straining against a locked-up gear or a seized trolley carriage. On the ChainMax 1000, the most common culprit is a broken plastic drive gear inside the motor unit.
How to Fix It
You'll need to replace the drive gear kit. First, unplug the opener and disconnect the red emergency release handle. 1) Remove the light bulb cover and the two screws inside that hold the motor cover on. 2) Slide the cover off. You'll see the motor and the gear assembly. 3) The plastic gear is likely shattered. The kit (often called a gear and sprocket kit) includes the new gear, a retaining clip, and grease. 4) Remove the old gear pieces, clean out any debris, pack the new gear with the provided grease, and snap it onto the motor shaft. Reassemble in reverse order.
If That Didn't Work
If the gear looks fine, the problem might be the trolley itself is jammed on the rail. Check that the rail is straight and the trolley moves freely by manually pulling the release cord and moving the door by hand.
Heads Up
When you order the gear kit, make sure it's specifically for the 3/4 HP ChainMax model. The gear for the screw-drive openers is different and won't fit.