usally 3 things,one is the sway bar bushings ,usally the outter ones. Or the lower or upper ball joints.And third wich i think might be your winner is the caster adjusting rod ball joint.On the lower control are there is a rod that goes to the rear (caster adjusting rod) and where it mounts to the body it has a ball joint.Once the boot brakes water gets in and wears it out