What was found
After Takeoff on Flight #3557, Red gear intransit light illuminated, also light in Gear Handle tried to recycle, unsuccessful. Light went out after 30 minutes. Flight diverted to DTW due to full load, repair and spare. Maintenance removed and repaired Landing Gear Selector Valve PN HTE9490-4. All work done IAW RJ85 MM 32-20. All checks good at this time.