What was found
DURING CRUISE AT FL 370 APPROXIMATELY ONE HOUR INTO FLIGHT, THE GREEN HYDRAULIC SYSTEM QUANTITY DROPPED TO ZERO. THE POWER TRANSFER UNIT AND THE NR 1 ENGINE DRIVEN HYDRAULIC PUMP WERE DISCONNECTED. FOLLOWED COCKPIT OPERATING MANUAL PROCEDURES AND CONTINUED TO DTW WHERE AN EMERGENCY WAS DECLARED AND AN UNEVENTFUL LANDING ACCOMPLISHED. MAINTENANCE FOUND THE NR 1 ENGINE DRIVEN HYDRALUIC PUMP LEAKING. REPLACED THE NR 1 EDP. LEAK AND OPERATIONAL CHECK OK.