What was found
RFD/DTW - FLT 1892 - CREW DID AIR TURNBACK DUE TO LANDING GEAR BEING FOUND EXTENDED AND LOCKED WHILE CLIMBING THROUGH FL 160. THE GEAR WAS EXTENDED WITH 3 GREEN, THEY VISUALLY CHECKED GEAR WAS DOWN. CFR CALLED OUT AND EMERGENCY LANDING PERFORMED WITHOUT INCIDENT. AFTER MAINT PINNED GEAR, NOTIFED CREW THE LT MAIN GEAR AND WHEELWELL WERE WET WITH HYDRAULIC FLUID. LT ACTUATOR RETRACT LINE FOUND LEAKING FLUID AT ONE OF THE SWAGED ENDS. LINE REPLACED AND LEAK CHK'S GOOD. AFTER ACFT FERRIED MKE, LANDING GEAR COMPONENTS INSPECTED WITH ASSOCIATED PLUMBING, NO FURTHER DEFECTS NOTED AND ACFT RETURNED TO SERVICE. (X)