I removed the shell from the chassis, ran it and noticed during the lower speed settings (1-3 out of 28) that the noise is not as loud, but is still there. At faster speeds, the noise doesn't appear to be noticable. From a visual perspective the drive train (gold color cams and plastic associated parts) doesn't seem to turn as smoothly as the drive train in my other loco (#6420) in comparison. That is until it runs at faster speeds (3+ out of 28) that it appears to run very smooth.
I might want to add that while taking off the shell I accidentally dislodged the front truck from the chassis and had to reassemble it, including repositioning the truck gear assembly back into the drive train plastic tube. Not sure if this did anything, but like I mentioned above, the buzzing noise was not as loud.
Any ideas on where to go from here? Is there anything that can be done to the drive train? lubricating the gears?
Thanks,
Steve