I have owned two Proto 2000 2-8-4s (first issue) which have both had the same problem. There seems to be a bind at a specific point in driver rotation. This happens at slow speed only, and clears up as speed increases. I have disconnected side rods at various drivers to try to eliminate any potential bind to no avail. By the time I get most of the rods disconnected, the locomotive is incapable of moving it’s own weight.
I sent one back to Lifelike (before they were acquired by Walthers) and it disappeared. Finally walthers made good on that one, but my other still has the problem.
Has any one here been able to correct a similar problem?
You might be looking at the wrong area. I had a problem with a Proto 0-8-0 and a Proto GP38 that had the same problem as yours. At slow speeds something would bind up and cause the loco’s to either stop or shake but once you sped them up they were fine. It turned out to be a little tiny piece of flash on a gear in both of my cases. Once they flash was removed both loco’s would crawl at a slow pace with no problems. It might be something to look at. I recently bought a few Proto 2-6-6-2’s and one also had a binding problem at slow speeds, it turned out to be from my own stupidity. The walkway between the loco and the tender was under the lip of the tender and not on top like it should have been. This caused a slight binding issue in the curves on my layout.