As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT TACHOMETER FAILED IN CRUISE FLIGHT. AIRCRAFT RETURNED TO BASE WITHOUT INCIDENT. TEAR-DOWN INDICATED TACH DRIVE SHAFT BEVEL GEAR FAILED AT OIL PUMP INTERFACE DUE TO OVERHEAT CONDITION. SEVERE GAULING OF SHAFT WAS NOTED. REPLACEMENT OIL PUMP COVER HAD OIL INLET HOLE FORTY THOUSANDTHS BIGGER THAN ORIGINAL.