What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS NOT DECLARED DUE TO: LOUD POP AND BANG IN NOSE GEAR BAY WHEN RETRACTING GEAR ON TAKEOFF, RECYCLED GEAR IN FLIGHT WITH MAJOR VIBRATION COMING FROM NOISE GEAR BAY IN FLIGHT. POSSIBLE THAT BAY DOORS ARE NOT CLOSING; AIRCRAFT AIR INTERRUPTED BACK TO AND LANDED SAFELY AT MIA. REPLACED NOSE GEAR RETRACT ACTUATOR, PER AMM 32-33-11. ALL REQUIRE TEST PASSED, PER AMM 32-33-00.