On Thu, 04 Feb 2016 09:04:19 -0700, Don Y
wrote:

Neighbor complaining of a rattling noise. Didn't take more
than a moment to determine chain is slack on his GDO.
Simple fix -- end of story.

But, got me wondering as to the potential downside of a
"slack" chain -- beyond the noise and *eventual* wear
on it and the drive bar from that rubbing.

OTOH, a *taut* chain is a recipe for premature wear in
the mechanism...

Which I why I've always bought Genie screw drives. My oldest one
lasted about 35 years of near daily use. Only repair was to replace
the engagement teeth ($10) once.