What was found
FLIGHT CREW REPORTED ON CLIMBOUT DURING GEAR RETRACTION, ALL GEAR INTRANSIT LIGHTS (RED) WENT OUT MOMENTARILY THEN CAME BACK ON AND STAYED ON (GEAR HANDLE IN UP POSITION). LDG SELECTOR TO OFF, NO CHANGE. LDG SELECTED DOWN, 3 GREEN LIGHTS PLUS NLG INTRANSIT LIGHT ON. LDG SELECTED UP, 3 INTRANSIT LIGHTS ON. LDG SELECTED OFF AND MAIN LDG DROPPED OUT. RECYCLED LDG, 3 GREEN LIGHTS PLUS NLG INTRANSIT LIGHT ON. VERIFIED NLG DOWN AND LOCKED THROUGH VIEW PORT. RETURNED TO ANC AND LANDED OVERWEIGHT WITHOUT INCIDENT. REPLACED NLG DOWNLOCK SWITCH DUE SHORTED. PERFORMED LDG RETRACTION TEST PER B727 MM 32-32-0.