Hey all, I have an older SD9, an Atlas 535xx series that came decoder ready. Installed a Digitrax way back when. This engine has been a real beast, very good puller although a tad noisy. Didn't bother me. Suddenly it has developed wheel slip, and can barely pull itself around the layout. Cleaning and rebuilding the trucks had no effect. On my test loop last night, I noticed it would occasionally jerk quickly, like a quick burst of freedom. I'm thinking a worm gear is cracked? Any ideas before I tear it all apart would be welcome. I've also noticed the wheels on this loco are noticeably "brassier" looking than the sister unit. They don't look worn, just a darker color.