What was found
(CAN) WHILE IN NORMAL CRUISE CONFIGURATION "MAIN TRANSMISSION" LIGHT ILLUMINATED. PILOT ACTIVATED PULSE CHIP DETECTOR SYSTEM AND LIGHT EXTINQUISHED. THE LIGHT RE-ILLUMINATED APPROX. 1.5 HOURS LATER. THE PILOT ONCE AGAIN ACTIVATED THE PULSE CHIP. DETECTOR SYSTEM, THE LIGHT EXTINGUISHED & REMAINED OUT FOR REMAINDER OF FLIGHT WHICH WAS APPROXIMATELY 45 MINUTES.MAINTENANCE PERSONNEL EXAMINED THE MAIN EXSN CHIP DETECTOR & EXTERNAL OIL FILTER. BOTH CONTAINED CONSIDERABLE AMOUNTS OF MAGNETIC METAL MATERIAL. AIRCRAFT SECURED & MAIN TRANSMISSION TO BE REPLACED.