What was found
ON GEAR RETRACTION RIGHT MAIN GEAR ILLUMINATED RED ON BOTH PRIMARY AND SECONDARY DISPLAYS. FOLLOWED QRH, CYCLED LANDING GEAR. AS SOON AS GEAR HANDLE DOWN, RIGHT MAIN SHOWED GREEN ON BOTH DISPLAYS (IE, NEVER IN TRANSIT). RETURNED TO HKG, DID NOT DECLARED EMERGENCY AND NO FUEL DUMP. REMOVED AND REPLACED RT MAIN LANDING GEAR TRIM CYLINDER PER MM 32-37-01-4. PERFORMED LANDING GEAR RETRACTION AND EXTENSION, ALTERNATION EXTENSION, FREE FALL OPERATION CHECK. ALL WORK OK AND INDICATION NORMAL PER MM 32-30-00. A/C OK FOR SERVICE.