Sounds like it is bouncng off the floor.
Try adjusting the down force.

Your door is closing too far. On the side of the motor unit you will find two controls. One is the 'up limit' and the other is the 'down limit'. With a small screwdriver turn the 'down limit' in the opposite direction of the arrow printed on the cover until the door stops at the garage floor but does not reverse to the open position.

Brickeye & Don -
Kudos to each of you. The up & down limits were actually on the bottom of the unit, but hidden by the light cover. After a few foolish attempts at playing with the up & down force screws (on the side), I realized where they were. The limit screw location has probably changed over the years. I'm in business, at least for now. And, the unopened replacement unit is on its way back to Sears.

Oh, I tried the tech # you mentioned in an earlier thread, Don. But because I had a pre-electric eye version, they wouldn't even talk to me. "I'm not UL-certified". I suppose eventually, I will be. Thanks for keeping me questioning.