What was found
AT APPROX. 15 MIN. INTO CRUISE (FL 33.0), #4 OIL QTY RAPIDLY DROPPED TO ZERO. FWD CAUTION PANEL LOW OIL PRESSURE LIGHT CAME ON. PRECAUTIONARY ENG SHUTDOWN ACCOMPLISHED PER ABNORMAL PROCEDURES. UPON INSPECTION FOUND GEARBOX N2 FULL OF OIL W/ TANK EMPTY.REPAIRED BY CHANGING PUMP, OIL TANK, CDS & STARTER SEALS. CHANGED PRESSURE RELIEF VALVE AS A PRECAUTION. NIL LEAKS ON RUN UP. OIL QTY MAINTAINED W/ NO EVIDENCE OF LOSS. A/C RELEASED TO SERVICE.