I'm trying to locate the source of an ear-shattering screech coming
from my dryer. The rear ball and socket were replaced just six months
ago. The front felt ring was replaced then, too.

I pulled the drum out and looked for signs of wear. The only thing that
looks suspicious is a bit of the rear of the drum, which looks like
something has been rubbing against it. It's left a wear ring, perhaps
an inch wide.

I looked inside the back of the enclosure to see what was rubbing
against it, and the only obvious candidate is an odd little piece of
plastic that juts out about two inches, screwed into the rear of the
enclosure. It's bright yellow. I can't imagine what it's purpose is. It
doesn't contact anything but the drum. Anyone have a clue? There is
another one at the front of the drum, but it's mounted in a different
orientation, and doesn't contact drum. It has to be removed before the
drum will slide out, but otherwise I don't see how it could be
functional in any way.

The only thing that came to mind is that perhaps it functions as some
sort of stop limit, as the felt wears down, to prevent the drum from
going too far out of alignment. But, as I said, the felt is new.