What was found
REPEAT WRITE UP IN CRUISE & DESCENT, LOUD RUMBLE OCCURS EVERY 5 MINUTES, SOUNDS LIKE IT IS ORIGINATING AFT OF FLIGHT DECK, GOES AWAY AFTER 1 MINUTE. C/W AP 18181, IAW 32-22-00 AND AMM 21-33-02, NO DEFECTS NOTED. ON VISUAL INSPECTION OF NOSE GEAR DOORS, NOSE GEAR DOOR SEAL PUT AIRPLANE INTO AIR MODE AND CHECKED LEFT AND RIGHT PACK EXHAUST DOOR, IAW 32-09-02. RT PACK EXHAUST DOOR FOUND OUT OF LIMITS BY .290 ADJUSTED AND TESTED, IAW 21-51-00. OPERATIONS NORMAL, NO FURTHER DEFECTS NOTED.