What was found
A TEAR-DOWN INSPECTION OF A 250-C20B ENGINE GEARBOX WAS PERFORMED. THIS GEARBOX WAS REMOVED FROM SERVICE DUE TO CHIP LIGHTS AND AN AUDIBLE WHINE HEARD OVER THE RUNNING AIRCRAFT. THIS GEARBOX WAS ASSEMBLED IN-HOUSE AFTER A 3500 HOUR OVERHAUL INSPECTION OF THE GEARS WAS PERFORMED BY AUTHORIZED REPAIR FACILITY. ALL BEARINGS INSTALLED WERE NEW FROM ROLLS ROYCE. THE PARTS, IDENTIFIED BELOW, WERE INSTALLED 141.3 HOURS AGO DURING THIS BUILD-UP. POWER TRAIN DRIVE GEAR SHOWED SIGNIFICANT WEAR ALONG WITH SPALLING ALONG THE DRIVING SIDE. THE COAST-DOWN SIDE WAS NORMAL.