What was found
IN FLIGHT, DURING CLIMBOUT FOR ABOUT 1000' FROM 15,000 TO 16,000 AT AN AIRSPEED OF 300KTS THE UPPER RUDDER BEGAN TO FLUTTER/PULSATE RAPIDLY LT AND RT. AFTER THE INITIAL PULSING, IT CALMED DOWN TO A SLOW CONTINUAL PULSATION BEING MORE PRONOUNCED ABOVE 300KTS AND INCREASING ABOVE 320KTS. SLOWED DOWN, THE PULSATION BECAME LESS NOTICEABLE; IT CONTINUED ALL THE WAY TO LANDING. NEVER RECEIVED AN EICAS WARNING OF A PROBLEM; THE SCHEMATIC OF THE UPPER RUDDER CARROT CONTINUED TO INDICATE THIS PULSING LT AND RT. UPPER RUDDER B WAS IN CONTROL. REMOVED AND REPLACED UPPER RUDDER ACTUATOR FROM THE VERTICAL FIN IAW MM 27-24-01, REV 41. OPS CHECKED SUCCESSFULLY IAW MM 27-24-01, REV 41.