My a$$ end get's all wiggly over certain roads and conditions, but it turned out to be a broken sway bar bracket. Right rear, not the D clamp, but the actual weld in bracket.
You might want to see if D clamp didn't slide out of the tab. I was at Ford the other day discussing my situation, and one of the techs said he's seen it a few time's where the D clamp has popped out of the tab insert. BTW, the D clamp is the bracket that goes over the bushing.
My two shiny pennies worth,
Mike