What was found
ON APPROACH, IMMEDIATELY AFTER DISCONNECTING THE AUTOPILOT, THE YOKE SHOOK FOR 2-3 SECONDS AND FELT SIMILAR TO A STICK SHAKER TEST BUT NOT AS INTENSE. THE SHAKING STOPPED BUT BECAME INTERMITTENT AND LESS INTENSE ALL THE WAY TO THE GROUND. AT TIME OF DISCONNECT, ALTITUDE WAS 800', AIRSPEED WAS ABOUT 120 KIAS, TRIM WAS NORMAL FOR PITCH & CENTERED FOR AILERONS. THERE WERE NO ANOMALIES ON DEPARTURE, CRUISE, OR INITIAL DESCENT. EVERYTHING WAS NORMAL UNTIL THE AUTOPILOT WAS DISENGAGED. IT DID NOT FEEL LIKE ANY OF THE CONTROLS WERE RESTRICTED OR JAMMED. LANDING UNEVENTFUL. REMOVED FROM SERVICE. REPLACED ROLL ACTUATOR. TEST FLIGHT GOOD. RETURNED TO SERVICE.