EE WAS BEGINNING A WORK AREA EXAM WHEN HE WALKED UP TO THE REPAIR AREA, WHEN HE NOTICED MECHANICS HAVING TROUBLE W/GEAR BOX AS THEY WERE MANUALLY LIFTING & LINING GEAR BOX ONTO SHAFT, SO HE ST OOD BETWEEN CONVEYOR & BEHIND SERVICE TRUCK TO HELP LIFT THE 215 LBS GEAR BOX. IN MIDST OF LINING UP KEY WAY ON SHAFT FOR GEAR BOX TO SLIDE ONTO, GEAR BOX BEGAN SLIPPING OFF SHAFT & WHILE STI