UP 3773: Modernizing a Scale Trains SD40-2

slemp_UP3773_20180430_092I think it’s reasonable to argue that the SD40-2 was the defining example of 2nd generation diesel locomotives in North America. They were purchased in huge numbers by most Class 1 railroads and have developed a reputation for reliability over decades of operation.  Today they’re less common on Class 1’s, but many are being rebuilt to extend their lives and quite a few are well into second careers on regional and short lines.  It has therefore been rather unfortunate that HO scale modelers have never had a really good plastic model of the SD40-2 (I’d argue that there’s never been a really good brass model either, because, well.  Brass.)  Many companies have made an attempt at the SD40-2, but most have gotten stuff wrong (Athearn, Intermountain) and no one has made a stab at the huge amount of variations that occurred over the twelve year production run (Kato).  Athearn could and should have put an SD40-2 in their Genesis line to go along with the GP models they’ve been releasing but they never did.

Therefore, it was no small thing when I cam home from work about a year ago to find a box from Scale Trains sitting on the stoop.  Inside, I hoped, was the SD40-2 so many of us have been waiting for.

It’s here!
It’s like October 1980 all over again!  Silver trucks, beacon and all.

The Model

A brief glance showed a pretty nice model albeit one clearly designed for the RTR market. The shell is well rendered and the proportions are correct. However some of the engineering is questionable, the parts were not properly cleaned up after being removed from the sprues and many of the details were installed poorly.  These aren’t deal-breakers, but they are frustrating.

Overall, the level of detail is impressive.  It’s just really unfortunate that everything has to come preinstalled as opposed to on a sprue or in bags.  I don’t think the blame for this lies with Scale Trains though.  I’d point to the laziness of the RTR crowd that gets bent out of shape when they have to press fit a part into a pre-drilled hole.  Even worse than the fact that the parts are  preinstalled is the fact that they’re almost all copiously glued into place. Because god forbid anything fall off in shipping.

The fit of the major components was a little wonky as well.  Something about the frame rail detail part causes it to look like it bows up. Extensive cleanup of flash and excess paint on both the plastic and metal frame components didn’t make it look much better.  The fuel tank also needed some work to get it to seat into the frame weight properly, some of the steps were crooked and the shell itself has an overly tight fit on the frame. I should point out here that for the most part I was able to fix these issues with a minimal amount of work and basic tools and skills but I’d rather I hadn’t needed to.

On the positive side of things, the paint is excellent.  It does in fact match Tru-Color Armor Yellow and Harbor Mist Gray.  The lettering is crisp and accurate. Best of all the paint strips easily with 91% alcohol and the lettering can be removed with the paper-towel-soaked-in-Solvaset trick, without disturbing the underlying paint.

As an early release from a very young company I think Scale Trains did a reasonable job on these.  More importantly I’ve found them to be happy to hear from customers and  incredibly receptive to feedback . As the two additional SD40-2’s I purchased from the second run have shown, they’re willing to make the necessary changes to improve quality control and fix design issues. If you want to buy an accurate model of an SD40-2 Scale Trains offering is the only choice worth considering.

The Prototype

I purchased a model of Union Pacific 3773 which was built in Oct. 1980 as part of EMD order 796345 for 40 units to become UP series 3769-3808.  According to Brian Bennett’s meticulously researched spreadsheet of SD40-2 phase variations: http://www.contrailroads.com/sd402phases/ (scroll to the bottom and download the actual database.  It’s an amazing piece of research) this is a phase IIIb2 unit.  Phase III units were built between Dec. 1979 and Dec. 1981 and saw the introduction of (among many smaller details) exhaust silencers (phase IIIa), Q-fans (phase IIIb1), and a strengthening rib across the middle of the battery box doors (phase IIIb2). These are in addition to changes that became standard in earlier phases such as corrugated radiator grills (phase 1b1 or 1c1 depending on whether the unit was UP or BN), clean cab/88″ nose (phase IIa1), etc.

Specific spotting features of this series include brake wheels instead of brake levers, extended range dynamic brakes (visible as an additional bulge around the exhaust silencer) and, as built, a beacon, class lights and silver trucks.  3773 did eventually get a waste oil reclamation tank cut in to the right rear of the fuel tank (http://www.rrpicturearchives.net/showPicture.aspx?id=3523941).  These were generally added during the UP’s SD40-2R Life Extension Program but that ended in 1999 without 3773 having been upgraded (See here for more info: http://utahrails.net/articles/sd40-2r.php).  I think it’s most likely that the waste tank was added after the LEP program ended. Since that was after my era I left it off.

Updating to 1997

Union Pacific’s SD40-2 fleet went through a number of changes over the years.  In order to make it accurate for my summer of 1997 era I did the following:

  1. It took awhile but I managed to break the model down into most of its component pieces.  After this photo was taken I ended up figuring out how to remove a few other sub-assemblies.
  2. I stripped the trucks and cut off the inboard sanding hose brackets as UP had removed these by the early 1990’s.
  3. I modified the outboard sanding lines by gluing the nozzle to the bracket and replacing the plastic hose with insulation from a micro bulb. I also removed and reattached most of the brake cylinders as they were crooked.
  4. I drilled out the front and rear class lights and removed the rear number boards as they will be painted over. I also removed the red “UP 3773” which will be replaced with just “3773” in white. The deck mounted MU cable receptacles were removed for repainting as well.
  5. The class light openings were filled with styrene rod to create blanks.
  6. The rear grab irons were painted armor yellow where appropriate. The front and rear headlights were painted gray, the number boards were painted, reinstalled and striped. “3773” was added in white on both sides of the long hood end.
  7. The spare knuckles were removed from the fuel tank.  New brackets were built and these were attached to the rear pilot. Their former locations on the tank were plated over. The MU receptacles were painted gray and reattached. The coupler cut lever ends were repainted white as were the step edges.
  8. The hand rail ends were painted white and the cans that UP mounted as dummy MU receptacles were fabricated from hollowed out styrene rod.
  9. New heralds were added below the road numbers on the cab sides (the Solvaset kind of melted this one :-/.) The edges of the mirrors/wind deflectors were painted gray.
  10. Pilot mounted ditch lights were installed. The red striping in the step wells was removed and warning decals were applied. Grab irons were added to the top of the plow and under and over the number boards. The beacon was removed and blanked with a spare C&C cover.
  11. Sergent couplers were built and pin lifter rings were fabricated. The Sergent’s are nearly a drop in fit and only need to have their shanks thinned slightly.
  12. The handrails and couplers were reattached.  The ditch lights were tested and lenses were added.  I don’t have a photo of the LED installation but there’s already a cavity in the frame for them. I just wired up a couple of Ngineering Micro LED’s, glued them to some styrene and stuck them to the frame.  The circuit board already has pads for ditch lights so I just wired them there.  The shell can be completely removed without needing to disconnect any wiring.

Painting and Weathering

I didn’t strip and repaint the entire model.  My goal with this project was to see if I could do a decent job updating it while still saving most of the paint.  Where I did strip paint (mostly on the underframe components) I grit-blasted and primed with Mr. Surfacer 1500 Black prior to applying the appropriate TCP color in lots of thin layers.  Painting like this made it pretty easy to get a very close match to the factory paint and any variation was covered up by weathering.

  1. The sideframes, traction motors and cab interior pieces were all completely stripped, grit blasted and repainted. I mounted the sideframes on a jig made out of styrene strip so that I could paint and weather them at once without needing to hold them.
  2. The sideframes were primed in black and then hit with a few layers of Tru-Color Harbor Mist Gray. Details were hand painted and various Mig or AK washes and pigments were applied along with a bit of Winsor and Newton oils here and there.  I blended the oils a bit and then applied some pigment wet.  This adhered the pigment nicely and created some texture in especially dirty areas.
  3. The cab interior was sprayed with base colors and then details were picked out by hand with Mig and Vallejo Acrylics.
  4. Washes and pigments were applied and carefully worked to give a used but not worn-out look.
  5. High voltage warning decals were taken from a Microscale UP decal sheet.
  6. I spent most of my time weathering the deck as this area tended to exhibit the most grime and wear. I started with a few colors of washes that didn’t flow particularly well.
  7. Eventually I was able to blend everything in.
  8. The magic really happened with I applied Mig Gunmetal pigments.  applying just a tiny amount and then burnishing the area with a paintbrush created a very satisfying worn metal look.
  9. After the deck was done the rest of the shell was smooth sailing.  I applied a few different panel line washes, painted the grills and added pigments sparingly overall but heavier in areas that would see a lot of exhaust residue.


Overall I’m pretty happy with what I was able to accomplish with this model.  There are a few things I’ll probably do different next time like replace the front MU hoses, that don’t hang properly over the plow, with brass ones and the molded chains with real chain.  I’ll also probably touch up some of the weathering and add more pigments once I have a layout and I’ll be able to keep handling to a minimum.  For now though, I’m calling it done.

I recently built a decent studio photography setup that’s a big improvement over what I was using (just my bench lighting) and I think I was able to get some halfway decent shots to showcase this model.  Click on the thumbnails for bigger photos and click the photo again for full size.  You’ll be able to see all my little screw-ups better than I can see them in person!

Enjoy and please let me know what you think. I’m always open to suggestions that I can apply to my next project.

16 Replies to “UP 3773: Modernizing a Scale Trains SD40-2”

  1. Chris,
    You did a nice job documenting what you did, and how. Thanks for sharing.
    I have a couple SD40-2’s which have been built from Athearn, GSB, and Kato models.
    I wish I could justify buying one of the ScaleTrains SD40-2’s, but so far, have not been able to justify a purchase, now if they did a high nose N&W version…. maybe enough to push me over the edge to get one.


    1. Thanks Brian!

      Scale Trains already did a Southern high nose, so I wouldn’t be surprised if they have an N&W in the pipeline.

      – Chris

  2. Hello Chris
    you did a splendid job on this loco, well researched and executed, it looks fantastic
    Terence Boardman

    1. Hi Chris
      Came across this build whist learning about scale railroad modelling as I am new to the scene and I’m in England so American railroad modellers are few and far between.
      I must say I am most impressed with your work and have learned a lot from reading your how to’s.
      I have one question for you if you’d be willing to help. What publication is the picture from that’s on your table when your modernising your Union Pacific SD40-2 from Scale Trains, the one that features BN 7845 and the SD40-2 blue print style drawing.
      Many thanks,

      1. Hi Mark,

        The page in question came out of the Model Railroader Cyclopedia Vol. 2: Diesel Locomotives: https://www.amazon.com/Model-Railroader-Cyclopedia-Vol-Locomotives/dp/0890245479

        The binding on my copy fell apart because I always had it open to the SD40-2 page. So I took the page out and put it under the piece of glass that I do some of my work on.

        As a source of accurate information I can’t really recommend the book. There are dimensional errors in some of the drawings and not a lot of useful text. That said, it’s fun to page through it occasionally.

        – Chris

  3. Chris, how did you attach the nozzle to the bracket? I might end up askig you a few more questions if that is ok?


  4. Hi Anthony,

    The nozzles are carefully drilled out at the back and a small piece of brass wire is inserted in the hole. The wire is then glued to the bracket with CA leaving just enough sticking out the back for the insulation hose to slip over.

    It’s all I could come up with at the time. The CA holds fine if the unit is running around a layout, but the nozzles tend to pop off during handling when the trucks get jostled. For my next one I’m going to have to figure out a way to mechanically fasten everything together.

    Ask all the questions you’d like.

    – Chris

    1. Hey Chris,

      Thanks for getting back with me on this. I have made the nozzle with the wire but wasnt sure how you attached the nozzle to the bracket.. I am going to study this more and if I come up with something I will share it with you.

      Well I just think I figured it out..Here is what I did, I took a #80 drill bit and drilled the end of the bracket (where you glue the nozzle to) and just slid the same wire used in the nozzle through this hole and its there without breaking off… I did have to drill it from the exterior area as that is the flat spot. The nozzle is on the inside with this but maybe try it and see what you think..

      Can I share the photos with you?


      1. Sure. If the photos are online, post the link here. Otherwise send me an e-mail.

        – Chris

      2. Did you get the email? If so what did you think of it?

      3. Yep, got it! Sorry I didn’t respond sooner, my wife defended her PhD recently and the graduation ceremony was this weekend. Her family was staying with us and I’ve only just made it back to both my e-mail and the workbench.

        The photos you sent are great and confirm the description you gave earlier. I had considered doing something similar but wasn’t sure I’d be able to get a hole drilled through such a small detail (the nozzles and pipes were difficult enough). Thanks for being the guinea pig and confirming it’s possible 🙂

        I’ve got my model back at the bench and already need to repair two of the sanding lines so I’ll try your method. Will report back once it’s done.

        – Chris

      4. Hey Chris, no problem, it was funny cause as I was writing down that I was going to try and find a way to attach them I got the idea.. so i hope it works for you.. i did use a pin vise with a needle in it to start the hole and drilled slowly until it went straight through.. anyway good luck and can wait to see show it works for you..


  5. Hi Chris
    I appreciate the info and I’ll be sure to check out those publications you recommended.

    Many thanks,

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