What was found
MLB DISAGREE WARNING IN FLT. AFTER ROTATION NLG DIDN`T RETRACT. RAN QRH & DECLARED AN EMERGENCY, LANDED SAFELY AT KORD & TAXIED TO GATE UNDER OWN POWER, NO OTHER ISSUES NOTED. QRH SUCCESSFUL IN RECTIFYING THE MLG DISAGREE. (FLIGHT 5103) NR 3 HYD ACCUMULATOR OPS CHKD GOOD. COMPLIED WITH LANDING GEAR AND HYD HEALTH CHECK. FOUND NLG SELECTOR VALVE LEAK, HYD SYS NR 3 FAILED PRESSURE DECAY RATE & PROXIMITY SESNOR NOT FULLY SECURED. CORRECTED & PEFORMED MULTIPLE SUCCESSFUL LANDING GEAR EXTENSION/RETRACTION SYSTEM AMM 32-30-00. OPS CHECK GOOD.