What was found
ON APPROACH LANDING GEAR DISAGREE WHEN LOWERING GEAR, CYCLED GEAR PER QRH AND STILL HAD DISAGREE (NOSE GREEN MAIN WHITE) PROCEEDED WITH QRH AND GOT 3 GREEN WITH MANUAL GEAR EXTENSION (FLIGHT 4234 - FILED CLOSED) TROUBLESHOT LANDING GEAR DISAGREE. PERFORMED EXTENSION AND RETRACTION OF LANDING GEAR. BOTH MLG STAYED UP AND LOCKED DURING EXTENSION. NLG EXTENDED TO DOWN AND LOCKED. REMOVED AND REPLACED MLG SELECTOR VALVE IAW AMM 32-32-10. PERFORMED EMERGENCY EXTENSION AND 8 SUCCESSFUL EXTENSIONS AND RETRACTIONS. OPS AND LEAK CHECK GOOD AT THIS TIME.