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Hi, everyone. I have a K-Line K3790-4015S Big Boy that I want to possibly perform some upgrades on. As is, the engine currently has TMCC and Railsounds.

I have been looking at various ERR upgrades in hope of gaining cruise control and better sound, as well as fix a few issues I’m having with the engine.

From the attached pictures, you’ll notice the smoke unit is removed. I also want to replace it with a better one and potentially add puffing synchronized smoke. Perhaps through GRJs super chuffer.

I also have an intermittent issue, where the engine refuses to run in reverse. I have already replaced the DCDR.

Finally, my rear elctrocoupler won’t work, despite replacing it with one from traindoctor and the sounds sometimes lose communication with the engine, despite replacing the tether with one from traindoctor.

Overall, I want to “revamp” this engine and get it running better than it ever has. As far as ERR upgrades go, I’m not sure what I need, given that this engine already has TMCC equipment. Can I possibly re-use some of the old equipment, or should I gut the engine and tender and start fresh?

I’ve done my best to take images of the engine and tender in their current configurations. Things like the chuff switch, I have no idea where they are located or how they would factor into an ERR upgrade. The tether also has 6 pins, but appears only 4 wires are used. If any of you want a picture of a different angle, I can provide it.

Any advice is appreciated.


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You can replace the DCDR (motor driver board) with an ERR CC-M. That's what I did when the DCDR in mine went out. It ran great after that but the sound was inconsistent due to the extra serial load (CC-M requires soldering serial RX to the R2LC connector). I added an amplifier for the serial based on @gunrunnerjohn's design and that helped some, but it still wasn't 100%. I eventually retired this one and purchased a new LionChief 2.0 Big Boy.

I haven’t worked on the K-Line Big Boy but have upgraded a dozen other K-Line TMCC engines with a Cruise M and never had an issue, same with other engines with wired tethers, only those with wireless tethers.

As for no reverse, check the 4 pin connector between the mother board and DCDR or swap out the R2LC if possible.


Not meant as a solution but only as a reminder, after the acquisition Lionel released this engine for S gauge with Legacy, Odyssey motors, cruise control, fan driven smoke and Legacy railsounds. All these items exist but it might be hard to acquire them all and put them in the three rail engine. Details and pictures inside the Legacy version are at

I'd consider testing the R2LC in another locomotive.  What you're describing sounds like multiple issues that all could be traced to the R2LC.  The ERR Cruise Commander M is a no-brainer to replace the DCDR, adding cruise will really be a big plus.

For smoke, I typically use the MTH steam smoke unit for upgrades to fan driven smoke.  I craft a mounting bracket out of aluminum or fiberglass, the K-Line "puffer" smoke unit leaves mounting posts conveniently placed for my ad-hoc smoke unit bracket.

If you want 4-chuffs/rev, I have just the product for you, the Chuff-Generator is a companion to the Super-Chuffer II.

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