Well, my Atlas SD-35 that I was so proud to call my first N scale engine seems to have a problem already. At slow to mid range speeds, it makes a high pitch squeelling sound. It still runs great, and the sound goes away at high speeds, but lower speeds just sound awful. Any ideas as to what it could be, and how to remedy it. or do I just take it back to the store. If I have to go inside, please recomend the tools I will need. I don't have anything small enough to work on these little guys yet.