I WAS DRIVING DOWN THE INTERSTATE WITH MY 2004 F-350 DUALLY WITH MY DUMP TRAILER ON THE BACK. I WAS HEADED DOWN A SLIGHT HILL WHEN THE STEERING WHEEL STARTED TO SHAKE. THE FRONT WHEELS STARTED TO MOVE BACK AND FORTH FROM LEFT TO RIGHT AND RIGHT TO LEFT VERY FAST BUT IN SHORT STROKES. THE SHAKING AND THE STROKES BEGAN TO GET LONGER SO THE WHEELS WERE TURNING MORE AND MORE EACH TIME THE WHEELS TURNED BACK AND FORTH.. THE SHAFT THAT COMES OF OF THE STEERING BOX THAT GOES TO THE PITMAN ARM SHEARED IN HALF. THIS CAUSED ME TO LOOSE CONTROL OF THE TRUCK BECAUSE I HAD NO STEERING. WHEN I HIT THE BRAKES THE WHEELS LOCKED COMPLETELY RIGHT, CAUSING ME TO GO OFF THE HIGHWAY, I HIT A BANK ON THE SIDE OF THE HIGHWAY HEAD ON, THEN THE TRAILER PULLED ME AROUND 180 DEGREES AND I ROLLED THE TRUCK AND TRAILER. *TR