What was found
AFTER SELECTING GEAR UP ON TAKEOFF, WE RECIEVED A GEAR DISAGREE CAS MESSAGE. THE TWO MAIN GEAR SHOWED UP AND LOCKED HOWEVER THE NOSE GEAR DISPLAYED AN AMBER DN INDICATION WITH THE GEAR HANDLE IN THE UP POSITION. QRH PROCEDURE WAS COMPLIED WITH AND RESULTED WITH THE GEAR INDICATION OF THREE GREEN. WE CONTINUED TO THE DIVERSION AIRPORT AND LANDED SAFELY. NO STEERING ISSUES WERE OBSERVED ON THE TAXI IN AND THE POST FLIGHT INSPECTION DID NOT REVEAL ANY ABNORMALITIES WITH THE GEAR DOOR LINKAGE. REMOVED LANDING GEAR MANIFOLD CHECK VALVE DUE TO NOSE WHEEL DISAGREE. INSTALLED CUSTOMER SUPPLIED NEW CHECK VALVE IAW AMM 32-30-25. OPS CHECK GOOD.