i know you heard the balljoint things already but have you had the LOWER LOWER balljoints checked?....they dont necessery have to have a play..but it could mean theat the grease is gone on eway or the other...even if the sleeve is not cracked.. what u can do is tell ur mechaning to lift the car push the sleeve back up very carefuly try not to damage it and spray some WD 40 on it..into it....if the sound stop...you are lucky and know what the problam is...either try to feel it up with proper grease..or change the balljoint..hopefully this will narrow down your search.