What was found
FIVE UNITS RUDDER TRIM REQUIRED IN NOSE LEFT DIRECTION WHILE IN CRUISE AT FL370 OAT -52 AND LEFT CROSSWIND OF 75 KTS. DURING THIRD ENCOUNTER WITH LIGHT TURBULENCE RUDDER MOVED TO THE RIGHT. RUDDER PEDALS ALSO DISPLAYED TO THE RIGHT. AILERONS COMPENSATED WITH 2 UNITS LEFT RUDDER TRIM WAS SLOWLY APPLIED UNTIL CROSS CONTROL CONDITION WAS CORRECTED. AFTER APPROXIMAETLY 8 MINUTES SITUATION SLOWLY CORRECTED ITSELF SWITCHING AUTOPILOTS CAUSED NO CHANGES. CHECKED WIRING FOR LEFT AND RIGHT YAW DAMP MODULE AND SERVO'S PER WDM 22-21-21 AND 22-21-11. OPS CHECK GOOD COMPLETED RUDDER CONTROL SYSTEM FREE PLAY CHECK PER S/B 767-27-0197 OPS CHECK GOOD PERFORMED RUDDER SYSTEM ROD END INSPECTION OPS CHECK GOOD FOUND YAW DAMP SUMMING ASSY WITH SHEARED RIVETS. REMOVED AND REPLACED SUMMING UNIT ASSY PER MM 27-21-18, OPS CHECKED GOOD.