My old Craftsman/Chamberlain 1/2 horse chain drive broke an extension spring last week.
Installed two new springs + new pulleys.
I tested it and balance is fine; almost no effort to raise/lower this heavy (145 lb.) old wood door
However I'm concerned that while the door is fairly quiet going UP, during last 1/3 of going DOWN,
it makes lots of noise, and **overhead track bows downward***.

This is a 2 car garage; 2nd door has similar chain-drive opener & no problems.
I notice that when 2nd door is closed, there is a maybe a 45 degree angle on
the bar that goes from trolly "slider" to the door, while on the "noisy" door,
that angle can't be more than 10-15 degrees.

Can this be where problem is?
Should I adjust travel of the slider on the trolly
(slider has 3 positions -holes- available,
currently set in hole closest to door, that provides least angle)

There are a lot of badly installed fixes and "upgrades" in this house,
--not me, from previous owner, I only do best work, and never ever make mistakes, ROTFL--
so would not be surprised that this c.1985 installation was ....junk.

.

BTW... Read several manuals, and found nothing about angles.
But, then again, the manuals I read were for later models where the portion that attaches to the door is shaped more like a letter J, while mine is a straight bar.
The "J" shape would tend to make you put that angle there.