What was found
(CAN) NOSE GEAR DID NOT RETRACT AFTER SELECTING GEAR UP ON TAKE OFF . NOSE LANDING GEAR DOWN WHEN WHEN GEAR DISAGREE WARNING MESSAGE OCCURRED MSG OCCURRED 28 SECONDS AFTER THE HANDLE REMAINED UP AND THE QRH ACTIONED A MANUAL EXTENSION WAS PERFORMED AND THE GEAR LEVER WAS SELECTED DOWN AFTER ALL GEARS INDICATED DOWN AND NORMAL LANDING ACCOMPLISHED . DURING WALK AROUND NOSE OLEO FOUND TO BE FLAT WITH PAX FULLY LOADED. SHOP REPORT FINALLY RECEIVED: SEALS, BUSHINGS, PACKINGS, RETAINERS, LOWER BEARING, UPPER BEARING, WORN BEYOND LIMITS. TORQUE LINKS AND PISTON/AXLE ASSY CORRODED. REWORK REQUIRED. GUIDE BLOCK AND UPPER TORQUE LINK DAMAGED. GEAR WAS INSTALLED SINCE AIRCRAFT WAS INTRODUCED TO THE FLEET. CSN 21554/CSO 9217 (TC# 20190815007)