MY 2001 BUS GIVES A CLUNK WHEN I TURN THE WHEEL FROM FULL RIGHT TO FULL LEFT OR VICE-VERSA- ALSO WHEN HITTING ANY SIZE BUMP IN THE ROAD- I'M SUSPECTING HEAD BEARINGS- IT HAS 35K MILES ON IT- WHAT IS INVOLVED IN CHANGING/TIGHTENING/ OR REGREASING THEM? I'VE CHECKED THOROUGHLY FOR ANYTHING ELSE LOOSE UP FRONT AND CAN'T FIND ANYTHING- ?