What was found
WHILE CLIMBING THROUGH 17K, GREEN HYD HI TEMP LIGHT ILLUM, COMPLIED W/ CHECKLIST, FEW MIN LATER FA REPORTED A HAMMERING SOUND FROM THE AFT CABIN, HYD QTY FULL, NO OTHER SYMPTOMS ON SHORT FINAL 'RUDDER VALVE' LIGHT ILLUM. COMPLETED PRE AND POST FIX HYD LINE TEMPS, REPLACED LANDING GEAR SELECTOR VALVE, INSPECTED TAIL SECTION FOR LOOSE OBJECTS NO DEFECTS. NOTED RUDDER VALVE LIGHT NORMAL W/ZERO GREEN HYD PRESSURE.