I broke my rear sway bar right where it bolts to the right rear control arm and it made noises during gear changes. But not sitting still. Far as rear end clutches making noise I haven't a clue but does not sound probable or likely. I have herd of busted control arm bushings being noisy, making clunking and slapping sounds just like my broken sway bar did. Your going to have to get under there and look around closely and see what you see.