What was found
AT 38,000, FT OIL QUANTITY ON THE NR 1 ENGINE DROPPED TO ZERO, OIL PRESSURE WAS IN AND OUT. WHEN PRESSURE DECREASED TO RED LINE, CREW SHUT DOWN THE NR 1 ENGINE AND FLEW ON ONE ENGINE FOR 20 MINUTES UNTIL ARRIVAL. MAINTENANCE ACCOMPLISHED MAGNETIC CHIP DETECTOR IAW AMM 79-21-05. INSPECTED ENGINE AFTER IN-FLIGHT. WINDMILLING IAW AMM 71-00-00. FOUND THE IDG SEAL LEAKING AND REPLACED THE SEAL IAW AMM 72-60-00. ACCOMPLISHED SATISFACTORY OPERATIONAL CHECK. AIRCRAFT WAS GROUNDED.