What was found
RDU/CLT - FLT 2327 - DURING CLIMB-OUT FROM CLT, LANDING GEAR WOULD NOT RETRACT. RECYCLED GEAR AFTER 2-3 MINUTES, GEAR RETRACTED. ON APPROACH, GEAR SELECTED DOWN, BUT MAINS DID NOT EXTEND. FOUR MINUTES LATER, RECEIVED THREE GREEN INDICATIONS. MADE SAFE LANDING AT CLT. MAINTENANCE REPLACED THE MLG SELECTOR VALVE. LEAKS AND OPS CHECKED GOOD. (X)