As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEVERE VIBRATION NOTED AND ISOLATED TO THE NR 3 GENERATOR. CREW SELECTED GENERATOR OFF, REDUCED NR 3 ENGINE TO IDLE, GENERATOR CONTINUED TO VIBRATE. SHUT DOWN NR 3 ENGINE AS A PRECAUTION, VIBRATION CEASED. AIRCRAFT THEN DIVERTED TO AN ALTERNATE AIRPORT. (M)