B767 Captain reported a gate return due to excessive force required to actuate the rudder pedals that was the result of a leaking rudder ratio module.

Narrative

My FO deadheaded into ZZZ and was aware first hand that there was a problem with the rudder pedals noted by the inbound crew. The inbound crew wrote it up and maintenance did their checks and were unable to duplicate the problem. After talking with the maintenance guy and he was running down the list of items they checked; I asked if they checked for a brake possibly dragging. He said he didn't notice anything unusual on his initial walk around; but went and checked anyway just to make sure to which he found no abnormalities. With everything looked at that the mechanic and I could think of and he couldn't find any problems; I determined the airplane was OK to fly unless it gave me a problem during the control checks; taxi or takeoff. After pushback; engine start and during my control check; I noted a significant amount of pressure was required to actuate the rudders and the left rudder required more pressure to actuate than the right. I wanted to make sure I wasn't being prejudiced by expecting a problem and asked my FO to actuate the rudders and tell me what he felt without telling him what I felt. After he did; he told me that he felt the same thing I did. After that; I called Dispatch and told my Dispatcher what happened and we agreed we needed to return to the gate which we did. Once we were in the gate; I called my Dispatcher back and talked to maintenance about what we experienced. After we put the problem in the logbook; the mechanic turned the electric hydraulic pumps on to do his checks and said the rudder pressure felt normal to him. That seemed wildly unusual considering what we experienced; so I asked him if I could actuate the rudders to see for myself. To my surprise; the pressure required to actuate the rudder peddles was normal. I told the mechanic that what we experienced was significantly different with the engines running than what we experienced with just the electric pumps. After that; we were released and sent to the hotel. Maintenance said there was a leaking rudder ratio module that was causing the abnormal rudder pedal pressure. We should all be critical of any abnormality with the airplane and investigate the problem thoroughly. My FO was solid and objective in his evaluation of the situation and came to the same determination as I did. If he had come up with a different conclusion; I would have listened to what he had to say to make sure I didn't overlook any details.