I changed my steering Servo to a metal gear high torque one and noticed that it "hums" almost like there is alot of pressure on it. So I adjusted it with the Steering Trim and could get the "hum" to go away, but as soon as I touched the steering again and it set back to center, it started up again. What I also noticed was that the Servo would only do that WITH the Transmitter on..the servo also made that "hum" while not even in the truck. So I came to the conclusion that its not a bad connection, nor stress on the servo.
Im not an expert, so correct me if im wrong guys...lol..I know ya will.