As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEPARTING OUT OF KJAC THE GEAR DISAGREE DISPLAYED ON THE EICAS AFTER TAKEOFF. THE LEFT GEAR WOULD NOT RETRACT. WE COULD ALSO FEEL AND HEAT THAT THE LEFT GEAR WAS STILL DOWN. RAN THE QRH CHECKLISTS, EXTENDED THE LANDING GEAR, CONFIRMED 3 GREEN “DOWN AND LOCKED” AND RETURNED TO KJAC. MX C/A: IN WORK, TROUBLESHOOTING WITH MX VENDOR AND ACCORDING TO MDC DOWNLOADS AND BAS-CRC, DOWN LOCK SENSORS NEED TO BE RIGGED. (~RTS 1/29)