What was found
AFTER TAKEOFF, NOTICED MAIN GEARBOX OIL PRESSURE DROPPING BUT INITIALLY STAYING IN ACCEPTABLE RANGE WITH NO SIGNIFICANT INCREASE IN TEMPERATURE. FLIGHT CONTINUED FOR A FEW MINUTES AND THEN PRESSURE DROPPED TO WARNING INDICATION LEVEL. EXECUTED AN UNSHEDULED LANDING WITHOUT INCIDENT. FOUND A LOSE OIL LINE AT THE TRNSMISSION OIL COOLER ASSY, INSPECTED LINE FOR DAMAGE, NONE FOUND. SECURED, TORQUED THE OIL LINE, SERVICED THE TRANSMISSION, PERFORMED A SERVICABILITY CHECK, GROUND RUN FOR 1 HOUR IAW MM WITH NO ABNORMAL INDICATIONS AND RETURNED THE AIRCRAFT TO SERVICE.