What was found
FLIGHT 3260 - SBP/LAX - PILOT REPORTED AFTER TAKEOFF THE LANDING GEAR WOULD NOT RETRACT. THE LANDING GEAR RETRACTED WHEN THE PILOT SELECTED OVERIDE. MAINTENANCE FOUND THE UPPER PISTON RINGS BROKEN CAUSING BINDING. MAINTENANCE REPLACED PISTON RINGS AND OUTER GLAND SEAL. A GEAR SWING WAS PERFORMED AND THE LEAK CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.