What was found
ON TAKEOFF OUT OF SNA WHEN WE RETRACTED THE GEAR THERE WAS A LOUD GRINDING SOUND AND EXCESSIVE VIBRATIONS. IN MEM ON FINAL WHEN WE SELECTED GEAR DOWN THERE WERE VIBRATIONS AND THE GEAR DID NOT EXTEND. THE DOORS SHOWED OPEN. ON THE GO AROUND THE GEAR CAME DOWN AND INDICATED NORMAL. WE LEFT THE GEAR DOWN AND RETURNED FOR A NORMAL LANDING. TROUBLESHOT PER ABOVE TSM AND FOUND NO FAULT/VIBRATION/GRINDING AFTER SWINGING GEAR MULTIPLE TIMES. WHILE INSPECTING NOSE GEAR FOUND NLG ACTUATOR LEAKING. TSM LIST ACTUATOR AS BEING A CAUSE FOR VIBRATION. REMOVED AND REPLACED NLG ACTUATING CYLINDER (1250). OPS CHECKS AND LEAK CHECKS GOOD. A/C OK FOR SERVICE AT THINS TIME.