As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ELEVATOR CONTROL HAS VIBRATION WHICH INCREASES WITH AIRSPEED ABOVE 250 KTS ANY DOWNWARD PRESSURE ON THE YOKE WILL CAUSE THE YOKE TO KICK BACK (AUTOPILOT OFF) (PTC ON/OFF MADE NO DIFFERENCE). REMOVED AND REPLACED ELEV LOUD FEEL CENTERING MECHANISM IAW DC-8 M/M 27-30-4, OPS CK GOOD ON GROUND. REMOVED AND REPLACED LT ELEVATOR CONTROL TAB IAW DC-8 M/M 27-30-2.