Boy, is my hand tired from typing..
When it is agitating, the thrust washer above the drive helix places the brake in a different postiion, with pressure on one side. when this thing splits or one of the rivets pops, it makes this noise. The only reason I came to figure this out was after some of us had replaced he transmission thinking it had a problem. When the clattering still happened after replacing the tranny, we had to take it all apart again to replace the brake.
I guess it comes down to economics. Since it is far cheaper to replace the brake, I would try it first. You would have had to tear it down anyway for a tranny replacement. I'm never right 100% of the time, especially when it comes to noises and such from a distance, so you have to take a lot of what I tell you on faith. I would hate for you to make a wrong move , so I try to cover all the angles.