THE INDICENT OCCURRED AS EE AND TWO COWORKERS WERE DOING AN IN-FRAME INSTALLATION OF THE FRONT HALF OF THE OIL PAN ON A CAT 3516C ENGINE. WHILE EE AND HIS TWO COWORKERS WERE LIFTING/HOLDING TH E OIL IN PLACE AND ATTEMPTING TO START THE BOLTS, EE FELT A PAIN IN HIS BACK.