Replacing rear trailing arm question.....

[Lapister]

Is there a definitive test to nailing a worn trailing arm (rear)? I've shook the suspension loaded/unloaded and can't see or hear any worn item. The only thing I noticed was when I took a large cresent wrench to it and rocked it back/forth it seemed to flex a bit at front attachment point. But it seems normal cause that's where the bushing is right? That annoying rattle only happens at slow speeds over bumps or when entering driveways. Hate to just throw parts at it.