B737 flight crew reported hearing grinding noise during takeoff and cruise from the trim wheel; resulting in the flight diverting to an alternate airport where they landed safely.
Synopsis
B737 flight crew reported hearing grinding noise during takeoff and cruise from the trim wheel; resulting in the flight diverting to an alternate airport where they landed safely.
Narrative
I've flown the KC-135; 747; 756; and the 737. Before today; I've only heard a trim wheel have a grinding noise once in the past 11 years. We caught it on the ground before a military mission; and it turned out to be frayed wires. I was the PF for the takeoff and cruise portion. We took off out of ZZZ headed for ZZZZ. As we climbed out; I began to notice a grinding noise every time the trim wheel moved. It didn't matter which system moved the trim wheel; the grinding was there. It was a noise I had not heard in my 2300+ hours from 800+ flights on the 737 variants. It concerned me. I voiced my concern about the grinding coming from the trim wheel; and the Captain could not hear it. I also asked if he was hearing the servo actuate. It sounded exactly like the servo for stowing the speed brakes. I had heard it twice already in the past few minutes and while I was asking the Captain heard it. I started looking through the manual for a procedure for the trim wheel grinding. I could not find one; and asked if the captain minded if I tried getting Maintenance Control to let us know if they had any ideas. Due to the nature of our concern and time delay from messages on ACARS; the captain utilized the call function so we could discuss with Dispatch and Maintenance Control on VHF. Maintenance Control's best guess was that it needed more grease and could be addressed in ZZZZ. The captain and I discussed it; and I expressed that I was uncomfortable continuing the flight due to a potential impending problem with the control system. I wanted it checked out. I believed that the safest course of action was to divert. The captain agreed that if one of us believed safety of flight was at risk; then we both needed to be on the same page; and a diversion to the nearest suitable airport was the most prudent course of action for a flight control concern. ZZZ1 was the closest airport that had a long runway at this point; so we Advised ATC and diverted to ZZZ1. The captain took over as PF once we started the diversion. We were now going to be doing an overweight landing. We referenced the diversion guide; the overweight landing checklist; and flew the approach to the longest runway; XXL; and the captain touched down nicely; and we gently braked using most of the long runway. The emergency vehicle looked over the brakes and indicated they were not hot. We taxied to the gate uneventfully. I should note that the servo sound from the throttle quadrant while airborne only occurred three times. I heard all three; the captain only heard it the last time. That was during the level off at cruise; which makes it unusual.
Second reporter narrative
FO reported trim wheel noise. I did not hear anything abnormal. FO insisted that he was hearing a noise and said he was uncomfortable and wanted to put the plane on the ground as soon as practical. We talked it through and decided to divert to ZZZ. No indications or lights supporting anything abnormal.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.