What was found
(CAN) GEAR WAS SELECTED DOWN, IMMEDIATELY ALL GEAR DOOR OPEN AS INDICATION, NLG AND RT MLG DOWN AND LOCKED, GREEN, LT MLG UNSAFE GEAR, RED. CONFIRMED THAT LT GEAR DOORS WAS OPEN BUT GEAR IN UPLOCK POSITION. APPROXIMATELY 90 SECONDS LATER THE GEAR MOVED TO ITS SELECTED DOWN AND LOCKED POSITION. UNEVENTFUL AND SAFE LANDING. MAINTENANCE REPLACED THE LT MLG UPLOCK ASSY, THEY FOUND THE WEAR GROOVE DEPTH MEASUREMENT OF LT MLG UPLOCK HOOK BEYOND LIMIT, 55 MM. AFTER SEVERAL SUCCESSFUL OPS TESTS OF MLG/NLG RETRACTION AND EXTENSION SYS, THEY BROUGHT THE ACFT BACK TO SERVICE.