As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
VIBRATION IN FLIGHT MOST PRONOUNCED AT 260KTS. COULD FEEL IN THE RUDDER PEDALS AND AFT CABIN. FA STATES THEY COULD HEAR A THUMPING SOUND AFT AND TO THE RIGHT. CREW SAID RUDDER MOVEMENT WAS STIFF ON THE GROUND AND IN FLIGHT. DIVERTED TO LAX.