What was found
CHS/CLT - FLT 1145 - AFTER TAKEOFF, THE LANDING GEAR WAS SELECTED UP BUT THE MAIN GEAR DID NOT RETRACT. THE LANDING GEAR WAS CYCLED AND THE MAIN LANDING GEARS RETRACTED. THE AIRCRAFT CONTINUED TO ITS DESTINATION AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE MAIN GEAR DOOR SELECTOR VALVE. (X)