Dare I say that Bacnmann’s N scale locos have improved a great deal in quality that what they made 25 years ago, but they may still have a long way to go. I used to own their original diesels…and every motor would burn out! They all now serve as “dummy” units, or with the headlight still installed, a “track tester”. Modern Spectrum diesels run well at first, and even smooter after about 12 hours running time. No burn ups, and they even draw LESS current when broken in. BUT…now the gears break! If your Bachmann runs noisy or jerky: one or more of your gears is broken. They break right down the axle shaft and up between two gear teeth. It is hard to see unless you have plenty of light, but it is there. I ordered replacement gears from Bachmann, but ultimately those gears snapped as well. This is a real problem the manufacturer needs to address.
Typical Bachmann crap. Buy an Athearn and be done with it!
Not an Nscaler, but have not heard of this. What are you using for lube as many greases and oils are NOT plastic compatible and will do exactly what you describe.
I use LaBelle Hob-E-Lube or LaBelle White Grease, both which are plastic compatible. I have used these on all makes, only Bachmann gears have split.
I know this is specifically for the Bachmann 0-6-0, but it can be adapted for others…
http://www.2guyzandsumtrains.com/Content/pa=showpage/pid=22.html
Northwest Shoreline might have replacement gearing. They have a catalog at there website. www.nwsl.com Good Luck. Sincerely, Mark.