What was found
LAX - FLT 1 - UPON GEAR RETRACTION AFTER TAKEOFF, A STRONG VIBRATION WAS FELT. GEAR WAS CYCLED, VIBRATION PERSISTED. FURTHER INVESTIGATION FOUND FORWARD LEFT NLG DOOR STUCK IN THE OPEN POSITION. INSPECTED NLG WHEEL WELL, FOUND NO DISCREPANCIES. FOUND LT DOOR LINK INOPERATIVE. REPLACED LEFT DOOR LINK PER MM 32-36-01. CHECK NORMAL. (M)