As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE, THE RT ENG HAD VIBRATION TO 5.0. DURING T/S IN FLT, THE ENG ANALYST AT HOME GOT A SMART SIGNAL THAT SHOWED A SHIFT IN F/F GET AND LOW N-2 ROTOR SPEED OCCURRED. CALLED THE MTC COORDINATOR WHILE ON THE RADIO PATCH AND ADVISED WHAT OBSERVED. ADVISED THE CREW TO RETURN TO ATL, METAL WAS FOUND IN THE TAIL PIPE AND ENGINE WAS REPLACED.