can be eather way check them frozen joints can damage the diff bearings. check them to see if they have g rese fittings. even if they can be lubed and no one did they are probly junk. if they are sealed YOU CAN REPLACE THEM WITH GREASABLE ONES i would not install anything else. ANY NOISE AT ALL I AM SHURE THEY ARE JUNK and DANGEROUS BAD JOINTS CAN COME APART IS THERE A THIRD CENTER U JOINT CHANGE ALL THREE