What was found
FLIGHT 2856, THE CREW NOTED THAT THE LANDING GEAR DISAGREE APPEARED ON EICAS AFTER TAKEOFF AND THE LANDING GEAR WOULD NOT RETRACT. NOTE, HYDRAULIC QUANTITY AND PRESSURE INDICATION NORMAL. MAINTENANCE REMOVED AND REPLACED THE LANDING GEAR ELECTRONIC UNIT, PERFORMED A OPERATIONAL CHECK, NO DEFECTS NOTED. THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.