What was found
DURING CLIMB, AIRCRAFT LOST HYDRAULIC QUANTITY ON THE NR 4 HYDRAULIC SYSTEM, WHEN THE LANDING GEAR WAS RETRACTED. AIRCRAFT RETURNED TO NRT AND LANDED WITHOUT INCIDENT. FOUND BROKEN SWIVEL JOINT ON THE RIGHT WING LANDING GEAR DOWNLOCK ACTUATOR. REPLACED ADP AND EDP ASSEMBLIES. REPLACED CASE DRAIN AND PRESSURE FILTER FOR ADP/EDP. OPERATIONAL CHECK GOOD.