What was found
NR1 ENGINE HAS A VIBRATION. LOSS CHANNEL 3 IN FLIGHT. RUDDER TRIM LOCKED UP IN FLIGHT AT ZERO POSITION AND FLIGHT CONTROL BECAME STIFF WITH SOME VIBRATION AFTER FLAP EXTENSION. PERFORMED VIBRATION CHECK ON ENGINE S/N 517620 NR1 POSITION IAW AMM 72-00-00 PAGE 503. HIGHEST READING WAS 4.39 AT 3525 RPM. FOUND TO BE ACCEPTABLE. REMOVED AND REPLACED GCU IAW MM 24-21-00. OPS CHECK PENDING. OPS CHECKED IAW MM 24-20-00 FOUND NORMAL. RUN ENGINE IAW MM 71-00-00. INSPECTED RUDDER TRIM SYS IAW MM 27-22-01, FOUND PULLEYS DIRTY. CLEANED AND LUBED IAW MM 12-21-04. RUDDER TRIM SYS OPS NORMAL. LUBED FLAP SYS IAW MM 12-21-04, OPERATION CHECKED FLAP SYS IAW MM 27-50-00. REMOVED AND REPLACED 2/3 REVERSIBLE PUMP IAW MM 29-22-01. OPS CHECKED NORMAL IAW MM 29-22-01. NO LEAK FOUND, NO VIBRATION.