As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: FLIGHT CREW REPORTED MAJOR AIRCRAFT VIBRATION CLIMBING THROUGH FL260, INDICTED AIRSPEED 320. FLIGHT CREW REDUCED THRUST AND VIBRATION DISSIPATED AROUND 290 INDICATED. NO ENGINE VIBRATIONS NOTED. MAINTENANCE FOUND THE LEFT HAND HORIZONTAL STABILIZER #6 ELEVATOR HINGE ARM END FITTING HAD EXCESSIVE PLAY AND REPLACED IT PER AMM 55-16-42.