https://ogrforum.com/...es-from-harmon-shops
From the fix applied, this sounds like a case of gears with holes on the large side of production tolerance, being pressed onto axles on the small side of production tolerance. Not every gear will move laterally on the axle, but when the above bad size match-up occurs the gear is going to move sideways on the axle.
The problem is actually that there is no spacer (i.e. throw-out bearing) to keep the worm wheel centered under the worm. Additionally, the bearing that is there is smaller than the axle bearing on the engineer's side of the locomotive. Over time, as that smaller bearing carves it's way into the axle bearing the side-to-side play increases, eventually allowing the worm wheel to either completely lose contact with the worm, or more likely, reduce the engagement of the two gears to the point where such a thin part remains that with any load, one or the other starts to lose its teeth.
There are a few videos on YouTube of this happening (gears grinding and all) and at least one poster on another forum that has a copy from a follow on run (from the original in 2011) that has been to Lionel several times for repair. Additionally, there is evidence from others' Legacy PRR H10s that the wear is beginning to take it's toll on a gearbox with the same, or nearly the same, design.
My intent in replying to this was not to hurt business for Beth - but rather to prevent her from having to deal with the backlash from dissatisfied customers. I like the Public Delivery Track and I've ordered from there before, and have a preorder there right now.
The most sinister part of this design flaw, is that it will only rear its head with use. Since the expectation from most people is that these engines last a lifetime (based on historical evidence) I think it's only fair to point out that these engines may not live up to that.
I also think that blowing these out is suspect after the problems with them are so well documented (including the most recent version of which I own a copy and have posted pictures of), the time limits of the current Lionel warranty period, and all of the evidence gathered in the other fairly recent thread.