B737-400 FLT CREW HAS R ENG VIBRATION AFTER TKOF; DIVERTS FOR LNDG.

Narrative

ACFT MAINT LOG HAD A WRITE-UP FOR 'POSSIBLE BIRD STRIKE; R SIDE ACFT/WING/ENG.' MAINT WAS CALLED OUT BY INCOMING CREW; AND VERIFIED BY OUR CREW. MAINT BY THIS TIME HAD THE LOGBOOK; SO I WAS BRIEFED THIS BY FO. DUE TO SECURITY; WE DID NOT HAVE FACE-TO-FACE WITH INBOUND CREW AND HAD NO FURTHER INFO. AFTER MAINT ARRIVED WITH LOGBOOK; I VERIFIED THE LOGBOOK AND ASKED MAINT TECHNICIAN WHAT HE FOUND. HE SAID HE DID FIND EVIDENCE OF BIRD STRIKE ON #2 ENG; ON FAN BLADE; BUT NO INDICATION OF ANY DAMAGE OR INGESTION THROUGH COMPRESSOR SECTION OR ENG CORE. VERIFIED DISCREPANCY WAS ADDRESSED PER MAINT PROCS ON LOG PAGE. TAXIED OUT FOR DEP. ON SPOOL-UP; ENG INDICATIONS WERE NOMINAL INITIALLY AND AFTER PASSING 90 KTS NOTICED VIBRATION METER ON #2 WAS ABOUT 3 UNITS AND STABLE; AND EGT ABOUT 830 DEGS AND STABLE; BUT APPROX 60 DEGS ABOVE #1 ENG LEVEL. AFTER TKOF; WE BOTH NOTICED A VERY SLIGHT VIBRATION AND LOUDER THAN NORMAL SOUND. WE CONTINUED TO MONITOR ENG INSTS AFTER CLB PWR SET AND RAN ATO CHKLIST FOLLOWED BY 'ENG VIBRATION' ABNORMAL CHKLIST. ENG VIBRATION NEVER EXCEEDED ABOUT 3.3 UNITS; BUT NEVER DROPPED BELOW APPROX 2 UNITS. REQUESTED INTERMEDIATE LEVELOFF; AND DECIDED AS CREW WE HAD POSSIBLE DAMAGE RELATED TO BIRD STRIKE WRITE-UP. NEXT CONTACTED MAINT CTL AND RELAYED INFO ON ENG PARAMETERS; PREVIOUS WRITE-UP; AND INTENTION TO PROCEED. NEXT CONTACTED DISPATCH; AND LATER RELAYED FROM MAINT CTL AND DISPATCH CONCURRENCE TO PROCEED. FO REMAINED PF WHILE I COORD WITH MAINT CTL; DISPATCH; FLT ATTENDANTS AND PAX. AUTOTHROTTLES ALSO TURNED OFF TO SEE IF IDLE THRUST HAD ANY CHANGE TO VIBRATION LEVEL. VIBRATION REMAINED AT 2-3 UNITS; INFORMED DISPATCH OF PROBABLE OVERWT LNDG; ALTHOUGH WE LOWERED GEAR AND DRAG 30 MI N OF SEA FOR VISUAL APCH RWY 34L. LANDED WITH WT OF 122300 LBS WITH SINK RATE BELOW 100 FPM; VERY NICE; SMOOTH TOUCHDOWN BY FO. USED AIII IN HGS TO MONITOR PARAMETERS.