B737-400
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Clearance
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
Yesterday we were flying ZZZ1-ZZZ. I was Pilot Flying. The flight was smooth and VFR going into ZZZ. ZZZ was landing Runway XX. The aircraft was downwind and I was at speed 230 and asked for flaps 1; speed 190. Once the flaps started coming out we noticed a light vibration which was consistent. Like driving down a bumpy road. The vibration continued until the gear came out and we slowed to 150. The rest of the landing I did not notice the vibration continue on landing. We landed; exited the runway and parked. Our Maintenance person went outside to do an inspection of the airplane and see if he could find the cause of vibration. The pilot monitoring and me also went out to see if we noticed anything unusual. Extended the flaps and the spoilers checking everything. Maintenance did not see an issue. The second flight going from ZZZ-ZZZ2 I was pilot monitoring. After lift off we noticed the same vibration very quickly. We retracted the gear and flaps on schedule. Then the PF (Pilot Flying) leveled off at 3;000 feet. We still had the same vibration and decided to return to ZZZ. Not exceeding 210 knots. The weather was still VFR and we landed Runway XX. We did not [request priority with ATC]. Once parked; our Maintenance person started a full inspection of the airplane. Into the inspection the elevator trim on the left of the tail was different than on the right. The Captain went into the cockpit and moved the flight controls up and down and the left trim tab was not moving the same as the right side. Maintenance personnel went up and inspected the trim tab on the left and found the control rod was not connected and it moved freely. Making a strange sound. Shortly after this we were told to head to the hotel so Maintenance could work on the issue. The aircraft recently sustained substantial damage in ZZZ3. The aircraft tail was damaged. I believe the two are connected. We came back and landed in ZZZ; very quick flight.
Air carrier First Officer reported flight control vibration in flight and did an air turn back.