As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE CLIMBING THROUGH, FL 140, THE FLIGHT CREW REPORTED LOSS OF OIL PRESSURE ON THE RT ENGINE. THEY IMMEDIATELY FEATHERED THEN SHUTDOWN THE ENGINE AND RETURNED TO THE DEPARTURE AIRPORT. THE MAINTENANCE REPAIR TEAM DISCOVERED THE RT ENGINE'S ALTERNATOR HALVES HAD SEPARATED, THIS CAUSED THE SEALED SPLINE SHAFT TO RETRACT FROM THE REDUCTION GEARBOX. THE END RESULT WAS COMPLETE LOSS OF ENGINE OIL OUT OF THE REDUCTION GEARBOX.