What was found
AFTER TAKEOFF THE CREW GOT A GEAR DISAGREE MESSAGE AND RAN THE QRH & QRC. THE DECISION WAS MADE TO DIVERT TO BHM. ATC DECLARED A EMERGENCY FOR THE CREW. AS A PRECAUTION THE CREW DID HAVE EMERGENCY TRUCKS IN BHM ON STANDBY DURING LANDING BUT THEY WERE NOT NEEDED. NO BRACE WAS CALLED BY THE PILOTS DURING LANDING. NO FURTHER INFORMATION HAS BEEN GIVEN. GEAR DISAGREE WARNING MESSAGE DURING RETRACTION / REMOVED AND REPLACED MLG SELECTOR VALVE IAW CRJ 900 AMM 32-32-10-000/400-801-A01. OPS/LEAK CHECK GOOD. NO FURTHER DEFECTS NOTED AT THIS TIME.