Thanks for the great tips fellows but I have already done those things, already being somewhat familiar with working on these motors. I can demonstrate that the squeal is not motor or axle related by gently pushing the locomotive along the track while holding the wheels so they can't turn, it still makes the same noise. I thought it might be the truck wheels, but oiling them didn't stop the noise. It isn't a continuous loud squeal, just sort of a soft periodic squeak really, when pulling a consist at speed I don't notice it for the rolling noise, but when just running the locomotive by itself it is obvious in the otherwise quiet room. I'll keep running it until I get the parts in, maybe it will straighten out on its own. When I got the loco it was obvious that it hadn't run in quite a long time, maybe it just needs a bit of exercise.
And yes, I always know where my towel is! 
