What was found
CREW REPORTED AFTER TAKE OFF AND GEAR RETRACTION,(DOWN LOCK LIGHTS EXTINGUISHED) THE HYD PRESSURE LIGHT AND GEAR UNLOCK LIGHT REMAINED ILLUMINATED. RECYCLED GEAR, SAME INDICATION. CREW ELECTED TO EXTEND GEAR, NORMAL EXTENSION (3 GREEN ILLUMINATED AND HYD PRESSURE LIGHT EXTINGUISHED). RETURNED TO BLOCK, LANDING UNEVENTFUL. MX PERFORMED SEVERAL EXTENSION AND RETRACTION TEST, COULD NOT DUPLICATE LANDING GEAR MALFUNCTION. AS A PRECAUTIONARY MEASURE, CLEANED AND LUBED ALL UPLOCK SWITCHES.