Generally that is caused by a bad bearing at the sprocket shaft. No amount of lubricant will correct the situation. It may quieten it down but the damage has been done.

I took off the cover and WD40ed it, so the squeak stopped, but as you say, it may be damaged where its just a matter of time till it fails?

Is the URL below the replacement part I'd want based on the p/n in the back of my owner's manual?

thanks ..

Here is a link that might be useful: replacement gear & sprocket assembly

I like WD 40 but its not much of a lubricant, its too thin for most jobs. I use to buy a spray lub made for motorcycle chains that worked pretty well. I think I read somewhere that the WD stood for water displacement and the 40 was their 40th formula they made, I don't know how much truth there is in that.

I have only seen brass bushings in older units. Is this a ball or roller bearing or bushing? Auto bearing grease has worked well on my opener�s bushings and worm gears. loger

I used the WD40 to at least stop the nasty squeaking for now. I ordered a replacement sprocket kit for like $25 off ebay. Just hope it can hold out till spring when I can replace it without freezing my butt off in the garage. I dunno what kind of bears are in the current one, I got it around 2000 ...

You ordered the right part. While you are at it replace both gears and slather the drive gear heavy with the supplied grease. You can use the remainder of grease on the t-rail.