As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT RETURNED TO BLOCKS AND SHUT ENGINE DOWN AFTER NOTICING THAT THE RPM GAUGE WAS UNSERVICABLE. UPON FURTHER INSPECTION FOUND THAT THE UPPER OIL PUMP GEAR, WHICH IS ALSO THE TACHOMETER DRIVE SHAFT. HAD SPLIT. THE PIECE WAS RECOVERED. AND THE GEAR / SHAFT WAS REPLACED WITH NEW. THE RESULTING DEFECT MAY HAVE ALSO CAUSED SOME WEAR TO THE BUSHING AND OIL PUMP HOUSING.