I've been struggling with my Athearn since I converted it to DCC. I replaced most of the friction type electricals with solder and connectors. I still have the "black" rail pickup going thru the truck/chasis pivot though. And this is where the problem seems to be. It seems to develop a high resistance after a while of running. This makes the engine jerk and surge, it also ends up getting to the point that the engine finally stops from electron starvation.
I had been trying different lubricants and was always lubricating the bronze(?) bushings that surrounds the axles as well as the truck/chasis joint. I figured the oils were causing my electrical issues and I tried silver conductive grease on the axle bushings and chasis/truck pivot the last time I took it all apart. This ended up working even worse than not using the conductive grease.
I mean all of these methods seemed to work for a while, but would start to act up after a few hours of running, the silver grease being the quickest to develop symptoms. This weekend I took it all apart, cleaned out the lubricants, and just gave the gears a smidgen of oil (with no oil on the pivot or axle bushings). This worked pretty well for a couple of hours then it started acting up again. :-(
Looking around the net, I've found where one guy placed a brash shim between the truck and the chasis. He claims it solved the conductivity problem between the truck and chasis on an Athearn. His theory is that it has something to do with the dissimilar metals. I'm going to nab some thin brass as soon as I can. Nothing to lose that's for sure. I'm trying to avoid soldering to the brass rivets in the truck, but I'm ready to resort to anything that will work for more than a couple of hours.
Anyone have any other ideas for me to try? The decoder wiring is all soldered and there are no problems with it, the main problem seems to be that juice just doesn't want to flow between the stamped steel in the truck and the pot-metal chasis.