A B727-200 WITH RPTED #3 ENG VIBRATION. ENG WAS INSPECTED AND CHKED PER THE MAINT MANUAL VIBRATION PROCS INCLUDING A HIGH PWR RUN. ENG WAS SIGNED OFF AS UNABLE TO VERIFY RPT. NEXT FLT OUT ENG FILTER BYPASS LIGHT CAME ON AND ENG SHUT DOWN.

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WE WERE SENT FROM OUR ABC BASE TO WORK ON WHAT WAS RPTED TO BE AN INTERMITTENT VIBRATION PROB WITH A JT8D ENG ON AN ACR AIRLINES ACFT. THE ACFT IS A B727-200; SHIP NUMBER XYZ. THE EXACT WRITE-UP WAS 'AFTER ROTATION #3 ENG START LEVER VIBRATED SEVERELY AND LOUDLY. THE #3 THROTTLE WAS ALSO VIBRATING TO A LESSER EXTEND. THIS WAS FOLLOWED BY A CALL FROM THE AFT FLT ATTENDANT STATING A VIBRATION COULD BE FELT AND HEARD. AFTER 45 SECONDS TO 1 MIN THE VIBRATIONS DECREASED. DURING CLB THE THROTTLE WAS MOVED TO IDLE AND RETURNED TO CLB PWR. OP APPEARED NORMAL AND ENG WAS SCANNED BY THE SO ON CLBOUT. MAINT WAS CONTACTED AND MAINT ARRANGED. REMAINDER OF FLT ENG OP NORMAL.' UPON OUR ARR INTO ZZZ WE INSPECTED THE ENG INLET AND EXHAUST AND NO FOREIGN OBJECT DAMAGE OR ANY OTHER DISCREPANCY WAS FOUND. WE OPENED THE ENG AND INSPECTED THE FUEL CTL XOVER SHAFT; CHIP DETECTOR AND ALL OTHER ENG COMPONENTS AND ONCE AGAIN FOUND NO DISCREPANCIES. WE DECIDED THE ENG WAS OK FOR SVC SO WE TOOK IT OUT FOR AN ENG RUN. WE RAN ALL 3 ENGS SEPARATELY AND AT THE SAME TIME IN AN ATTEMPT TO COMPARE THROTTLE AND CUT OFF LEVER VIBRATIONS. WE RAN THE AFFECTED MOTOR AT THE TKOF PWR FOR 5 MINS AND FOUND NO VIBRATIONS OUT OF THE ORDINARY. WE RETURNED TO THE GATE AND SHUT DOWN ALL ENGS. WE THEN AGAIN STARTED THE #3 ENG AND STILL NO DISCREPANCY. ACFT LOGBOOK WAS SIGNED AND ACFT RELEASED FOR SVC. WE RETURNED TO ABC. THE ACFT DEPARTED TULSA ON THE MORNING OF JUN/XA/99; ON A FLT TO SALT LAKE CITY. ENRTE THE CREW GOT A #3 ENG OIL FILTER BYPASS LIGHT. THEIR WRITE-UP WAS EXACTLY; 'OIL FILTER BYPASS LIGHT ILLUMINATED INFLT. ALL PARAMETERS INDICATED NORMAL. ACCOMPLISHED ENG FAILURE/PRECAUTIONARY SHUTDOWN PROC. FLT ATTENDANTS NOTICED VIBRATION IN AFT PORTION OF AIRPLANE PRIOR TO SHUTDOWN.' THE FLT WAS DIVERTED INTO XXX WHERE THE ENG WAS REPLACED.