EMPLOYEE WAS UNDER THE TEREX 3360 HAUL TRUCK INSPECTING DRIVE LINE BOLTS. AS MECHANIC WAS COMINGFROM UNDER TRUCK ON THE LEFT SIDE, HE RAISED UP TOO QUIKLY, NOT CLEARING HIMSELF OF TRUCK, BUMPI NG HIS HEAD ON THE STEERING HYD. TANK ON THE TRUCK. INCIDENT CAUSED MUSCLE SKELETAL PAIN.