What was found
SULFUR ODOR IN FLIGHT DECK AND CABIN. VERIFIED ODOR COMING FROM THE APU BLEED AIR. TURNED OFF APU BLEED AIR AND ODOR DISSIPATED. GROUND RAN BOTH ENGINES WITH BOTH BLEED SOURCES ON. NO ODOR FOUND. VISUALLY INSPECTED & FOUND EVIDENCE OF OIL LEAK AROUND APU GENERATOR/ GEARBOX OUTPUT SHAFT. REPLACED APU GEARBOX OUTPUT SHAFT SEAL IAW AMM 49-90-17-000-801 & TR 49-040. APU GENERATOR OPS CHECK GOOD. NO LEAKS NOTED. C/W OPERATION TEST OF ECS TEMP CONTROL. REF AMM 21-61-00-710-803. NO SULFUR SMELL IN FLIGHTDECK/CABIN. RETURNED TO SERVICE.