What was found
(CAN) WHILE IN CRUISE FLIGHT THE PILOT GOT AN INDICATION OF NO TRANSMISSION OIL PRESSURE ON THE WARNING LIGHT AND PRESSURE GAUGE. HE PROCEEDED TO LAND. WHEN HE ROLLED THE THROTTLE TO IDLE THE BLADE SLOWED QUICKER THEN NORMAL HE THEN SHUT THE ENGINE DOWN AND THE BLADE STOPPED IN LESS THEN A MINUTE. THE MAIN TRANSMISSION SEIZED AT THIS TIME. IT WAS FOUND THAT THE TRANSMISSION WAFFER FILTER GASKET HAD BLOWN OUT AT HE BOTTOM. WHEN THE NUT TORQUE WAS CHECKED ON THE FILTER HOUSING ALL FOUR NUTS WERE FOUND BELOW THE SPECIFIED TORQUE VALUE. THE FILTER HAD BEEN CLEANED 2 DAYS PREVIOUSLY. AN O/H TRANSMISSION AND MAST WERE INSTALLED AND THE ACFT FLOWN OUT.