What was found
WHILE MOVING THE FLAP MOTOR AND GEARBOX ASSY PER STC SA474NW, DISCOVERED DAMAGE TO THE FLAP DRIVE TORQUE TUBES, PN 31B164-3. UPON REMOVAL OF THE TORQUE TUBES, DISCOVERED WEAR ON THE TUBES WHERE THEY PASS THROUGH THE FUSELAGE. THE SEAL ASSY (PN 21158-0013, RETAINER ASSY, PN 34172-11) FOR THE LT TORQUE TUBE HAD FAILED CAUSING THE TORQUE TUBE TO RUB AGAINST THE RETAINER HOUSING OF THE SEAL. THIS CAUSED A GROOVE TO FORM INTO THE TORQUE TUBE. THIS GROOVE WAS APPROX HALF THE WALL THICKNESS OF THE TUBE. THE RT TORQUE TUBE SEAL WAS FOUND INTACT; THE TUBE WAS STARTING TO FORM A GROOVE AT THE SEAL CONTACT AREA. THE TUBE SHOWED SIGNS OF WEAR CAUSED BY MOVEMENT OTBD AND INBD BETWEEN FLAP JACK SCREW AND FLAP GEARBOX.