Shell install attempt #2.
Okay, the back of the shell now drops all the way down, but, the front won't go all the way down and is doing and bit of a teeter-totter. I determined that the heat-shrinked, solder joints for the speaker wires is the issue. You can see that in this photo of the brown speaker wires running across the top of the speaker.
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This one took some head-scratching to figure out.
I decided the wires had to come up a different way, so, the first thing I had to do was pry out the 6-pin wiring harness to allow me to remove the speaker and work on it. Then, I peeled the wires out from the slots in the side of the speaker. I then cut a new groove/slot in the corner. Like this:
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Update time!
The first thing I did was decide to abandon the idea of installing fwd and rear gyralights. Trying to stuff two additional wiring harnesses and micro-connectors into what is already a tight spot made me decide that I shouldn't make my first switcher (SW1500) install any harder than necessary. I figured that I could learn from this first SW1500 install and attempt to install gyralights on any second SW1500 I attempt to do down the road. This turned out to be prescient - more on that later.

Here's what the everything looks like after being wired up.
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Here's another view with the pigtails connected to the shell.
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Howdy Rob!

One question: Were you able to successfully solder the wire to the sideframe after drilling the hole? Your photo shows it prior to soldering.

It's been awhile since I posted that. While I don't specifically remember having an issue, it is a sizeable piece of metal that acts as a heat sink, so you have to make sure you get it hot enough for the solder to be effective. That tunnel motor is still running great.

Good luck!

Wow. I wish I had found this post two months ago.

It is the exact issue I am having on a brand-new Athearn EMD SW1500 locomotive.

I have been tearing my hair out for some time trying to figure out this electrical conductivity problem.

I also use RailPro and have used this forum to look up other things but found this specific post through Google while researching the stuttering issue as it relates to Athearn's pickup design.

After rewiring and soldering the pickups to the tops of the gear towers multiple times and cleaning and lubricating the wheels, axles, square phosphor-bronse bearings and the metal sideframes (as well as going through FOUR different RailPro modules, two LM-3S-21s and two LM-3Ss to be sure they weren't defective), I came to the conclusion that it must be poor electrical contact with the phosphor-bronse bearings on the axles as they sit in the square notches of the metal sideframes. Nothing else made sense.

I even went so far as to make additional pickup connections. First with wire soldered to the bearings and then stiffer phosphor-bronze wire normally used to make handrails. See attachment.

Still, the issue has persisted.

It's difficult to solder to the metal sideframes directly so I was going to try a better connection to the grommet. It seems from your experience, the grommet itself may very well be the issue here.

One question: Were you able to successfully solder the wire to the sideframe after drilling the hole? Your photo shows it prior to soldering.

I have found the sideframes to be very difficult to solder to. Just wondering how you did it.

Thank you for posting your solution.

Rob S. "Sieggs1"

Philosophy does not equal reality. There are a multitude of examples of trains around the world that are pushed by the locomotive in one direction of the journey. Of course, we are talking passenger trains, like the OP post is about. If I looked into it deeper I'm sure I be saying 100% of the models of trainsets here that have a locomotive at both ends have a powered model at one end only, the locomotive at the other end is a dummy.