Captain reported landing gear would not retract when selected after take off. The flight crew requested vectors back to the airport and made a precautionary landing.

Narrative

The purpose of the flight was a maintenance test flight. The airplane had just finished the 12; 24; 48; 110 month inspections. This was a 'Shake Down' test flight to verify all systems were operating properly after extensive maintenance as well as to perform a maintenance required Air Driven Generator (ADG) flight check. On Take off when the landing gear was selected up; the nose and left main retracted normally. The right main gave us a Gear Disagree message. I called for the QRH procedure and called the Mechanic who was riding along (to verify the ADG check) to come up front so he could see what was going on and to verify what we did as we went thru the QRH. I flew the aircraft and took the radios while my First Officer and Maintenance Tech went through the QRH procedures. This called for a manual extension of the gear. I notified Approach that we had a gear indication and requested to not climb and to have extended vectors back to ZZZ while the QRH procedure was performed. We landed in ZZZ without incident and taxied to the Maintenance Facility we left from.