Thanks for taking the time to try to help me out. I was extremely amused with this--I know what an o'ring is, but I will admit I have never heard of one being "chunked out". I am thinking it means it is worn out, broken?? Where will I find this and is is realistic to think that I can open up the opener to replace the o'ring? I will have my friend who can do this but he does not have experience with openers. I am not certain it is the opener. If this helps--it is the second half of the down that the shaking/vibrating of the door is bad. I visited what I refer to as "the manly" part of the hospital where I work---I go for tips and advice--like this site---he said to check the metal pieces that go up into the ceiling and attach to the joist to see if it is tight. Thought that would be it---made sense. They were real tight.