EMPLOYEE WAS WORKING IN MOBILE MAINTENANCE SHOP AS AN ASSISTANT. A MAINTENANCE TRUCK WAS ON THE HOIST AND EMPLOYEE WAS SERVICING FRONT DIFFERENTIAL WITH/80/90 GREASE. FILLING WAS COMPLETE AND HE DUCKED TO GET PAST REAR DIFFERENTIAL AND THEN WALKED INTO THE SHOCK ABSORBER MOUNT, WHICH IS LOCATED UNDER THE REAR AXLE. CUTTING THE TOP OF HIS HEAD.