What was found
DFW - FLT 3521 - AFTER TAKEOFF BOTH MAIN GEARS INDICATED UNLOCKED WITH GEAR SELECTED UP, SELECTED GEAR DOWN, GOT 3 GREEN LIGHTS. RETURNED TO DFW LANDING WITHOUT INCIDENT. MAINTENANCE CHECKED ELECTRICAL SYSTEM WITH NO DISCREPANCIES NOTED, CHECK MAIN GEAR ACTUATORS. FOUND LEFT ACTUATOR INTERNAL LEAKING. R/I'D LEFT ACTUATOR AND PERFORMED RETRACTION TEST SATISFACTORILY, ALSO PERFORMED FLT FLEET SATISFACTORILY PRIOR TO RETURNING A/C TO SERVICE. (M)