What was found
AIRFRAME SHAKES AT HIGHER SPEEDS UNLESS PRESSURE APPLIED TO RUDDER, APPLYING A CONSTANT LOAD TO IT. IN 5 PREVIOUS OBSERVATIONS OF IDENTICAL SYMPTOMS, THE ISSUE IN EACH CASE TURNED OUT TO BE WORN RUDDER ACTUATORS. INSTALLED LOWER RUDDER ACTUATOR. TORQUED AND HOOK UPS FOR ALL 3 ACTUATORS , ALL STEPS EXCEPTS 2 E 14 AND 15 (SECONDARY SAFETY BOLTS THROUGH THE CENTER OF HOLLOW ACTUATOR BOLTS). STILL REQUIRES OPS CHECK AND RIG BEGINNING AT STEP H. AMM 27-24-11-04-02. CLOSED RUDDER ACTUATOR CLOSEOUT PANEL AND RRUDDER HINGE PANEL IAW S.M.P., OK FOR SERVICE.