What was found
ACFT DEPARTED AND ENROUTE, NR 3 ENGINE HAD SEVERE VIBRATION AT FLIGHT LEVEL FL300. ENGINE INSTRUMENTS INDICATED NORMAL AND NO MASTER WARNING SYS LIGHTS ILLUMINATED. CREW SHUT NR 3 ENGINE DOWN AND FOLLOW ABNORMAL PROCEDURES TO FLY WITH ON ENGINE INOPERATIVE TO MINIMIZE EFFECT AND POSSIBLE DAMAGE FROM VIBRATION. LANDED SAFELY. AFTER INSPECTION, APPEARED THERE WAS AN INTERNAL BEARING FAILURE ON SHAFT OF NR 3 ENGINE. ENGINE REMOVED AND A RENTAL ENGINE INSTALLED DURING EVALUATION AND REPAIR OF ORIGINAL ENGINE.