What was found
FLT 736 - CVG - NR 1 ENGINE OIL QTY WENT TO ZERO AND PRESSURE FLUCTUATING PLUS/MINUS PSI. NR 1 ENGINE SECURED (SHUT DOWN) IN FLIGHT. TEMPS WITHIN LIMITS, 13 MINUTES OF WINDMILLING, POSITIVE OIL PRESSURE THROUGHOUT LANDING. REPLACED CRACKED OIL PRESSURE LINE AT FUEL/OIL COOLER PER MM 79-21-0. REMOVED OIL FILTER AND INSPECTED FOR METAL DUE TO INFLIGHT SHUTDOWN PER PWA MM 72-00, NONE NOTED. REPLACED OIL FILTER. REPLACED NR 1 ENGINE GEARBOX BECAUSE HELICOIL STRIPPED OUT OF GEAR BOX WHILE INSTALLING BRACKET ON NEW OIL LINE. (M)