My Athearn GP38 will make a screeching noise every so often. If I stop the train and start it again, the noise may disappear temporarliy. I've cleaned the wheels, track and visually inspected while it was running without the body but did not see anything binding. Loco has been used very little. I have not had such problems with my other engines. Does anyone have any suggestions. Yes, I know the above description has very limited information but anything would help. Thanks!