As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED LOSS OF INSTRUMENT VACUUM FROM REAR ENGINE DURING BEFORE TAKEOFF GROUND RUN UP. INVESTIGATION REVEALED THAT THE VACUUM PUMP WAS STILL SERVICEABLE. FURTHER INVESTIGATION REVEALED THAT ALL OF THE GEAR TEETH WERE SHEARED OFF OF ONE OF THE BEVEL GEARS WHICH DRIVES THE VACUUM PUMP.