What was found
AT FL380, 1 HOUR BEFORE DESTINATION, YOKE CENTERED, DISENGAGED AUTOPILOT AND HAD TO PUT IN LOTS OF RIGHT RUDDER. ALL INDICATIONS WERE CENTERED EXCEPT, INOPERATIVE RUDDER TRIM READ LEFT RUDDER 2 UNITS. PERFORMED RUDDER AND RUDDER TRIM OPERATIONAL TEST IAW AMM 27-21-00, NO DEFECTS EXCEPT RUDDER TRIM INDICATOR CURRENTLY ON MDDR, ALSO REFERENCE AMM 27-01-00/501 RUDDER TRIM LIMITS OK FOR SERVICE.