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Athearn Tunnel Motor Detailing
Detailing your new Athearn Tunnel Motor
by Joe Snoy & Steve Orth
Don Strack's Site Data


Detail Addenda

MARS Lighting

   From Don Strack's Website:

The Athearn model represents the second group (below), however the first group is almost identical and would provide more numbers to model.

D&RGW 5341-5355 (15 units)

* D&RGW 5356-5373 (18 units)

The first delivery (5341-5355) was built in 1974 and was equipped with the 81" nose, ratchet brake lever and short slots on the battery box. The Athearn model is very close with the 81" nose and ratchet brake lever, but has longer slots on the battery box which I consider a "minor" difference when you see actual pictures of these locos.

The second order (5356-5373) was built in 1975 and was equipped with the 81" nose and ratchet brake lever, but had longer slots on the battery box. The Athearn model matches this delivery exactly. However loco 5357 was involved in a wreck and rebuilt with a 88" nose and wheel-style brake handle similar to the follow-on deliveries.

The 3rd, 4th and 5th TM orders (5374 thru 5413) have a brake wheel in place of the ratchet brake lever and an 88" nose - these are a noticeable difference. The nose light for the 4th order (5374-5385, built 1977) protrudes a noticeable amount (a box-like fixture), but the 5th order reverted to the "normal" DRGW nose light style. These would not be a good match for the Athearn model in my opinion.

With regard to the the Positive Train Contol (PTC) "box" located behind the cab door on the left side, this was a modification added to all units in the mid '80s so that is not really important when selecting a loco number.

In my opinion any number from 5341-5373 would be appropriate for the Athearn model. Steve may have some additional comments.

Not so quick there. There are two other discrepancies between the model and the second order. They are on the front half of the locomotive. It is common to all EMD -2 locomotives of that time frame.

    Super-detailing Athearn's Rio Grande SD40T-2 - courtesy of Joe

Here is a rundown on what after-market detail parts can be added to the Athearn model and a few changes that can be made to make it a more accurate replica of the Rio Grande's second order, units 5356-5373 or convert to first order 5341-5355 .


  • Replacement plow w/ open doors: DW 155
  • Coupler lift bars & brackets: DA 2211 gives you both, DA 2212 for the lift bar alone or OMI 9151 (OMI 9152 if modeling 5341-5355) Since the plastic brackets are very fragile, you may want to use the brass ones instead: DA 102213
  • Train line air hose: DW 302
  • MU hoses: DA 1508 or DW 294 or OMI 9349
  • MU stand on front deck: DA 1505
  • MU cover on rear pilot: DA 1505/1507 receptacle & cover only (Cut in half horizontally and snug up against the underside of the anticlimber.)
  • Drop step: DA 1404
  • Coupler lubricator cup & line: scratch from styrene rod, shim brass and very fine wire
  • Diagonal lift slots: drill out & carve to shape
  • Trim the lower corners of the hose tray on the rear pilot at 45
  • Bottom corners of pilot should also be at 45 instead of notched: fill in with sheet styrene, then trim at 45
  • To model units 5341-5355 from the first order fill in the notches in the top corners of the front pilot with sheet styrene.


  • The model comes with a replacement Pyle Gyralite. For the as- delivered Mars light: DA 1007 or DW 290 Note: the slope on the bottom of the nose notch looks a bit shallow, so you might want to make it a bit steeper by slicing it with a knife while you're at it.
  • Sand filler (very shallow on model): DA 3001, or just use DA 1505/1507 MU cover


  • Vents: DA 1902 or DW 122, add as per photos of individual units
  • Wind deflectors/mirrors: DA 2312
  • Windshield wipers: AL 29200
  • Step under number board: short length of bent wire
  • Blue flag bracket: short length of bent wire, center of cab side beneath window on engineer's side only
  • Leslie Tyfon 3L horn if your unit got a replacement: DW 190 or PIA 155
  • Replacement Nathan M3 horn should you break the one supplied: DW 186 or OMI 9004 (both brass)
  • Replacement Sinclair antenna should you break the one supplied: DA 101803 (brass)

    Long Hood

  • Electrical cabinet air filter cabinet: CAN 1903 (The supplied cabinet has an ugly parting line in the outside face.)
  • Lift rings: DA 1101 plastic, 101101 brass, 2206 formed wire
  • Lift tabs: DA 1104 plastic or RF 1015 brass (two at top of rear end)
  • Rear sand filler: DA 3001, or just use DA 1505/1507 MU cover
  • Right rear corner grab: form out of wire
  • Scribe & burnish centerline weld bead in three roof panels behind dynamic brake insert
  • Add paired rivet batten strip to cover groove between first and second roof panel behind dynamic brake insert: RF 6206 (photoetched brass)
  • Marker light brackets at rear rear corners at same level as classification lights: fashion from small bits of styrene
  • Walk light slits at rear corners and on rear end: small strips of white or silver decal
  • ACI label & plate: decal on .005 styrene or shim brass on fourth handrail stanchion behind cab

    Deck Sills & Underframe

  • Small filter beneath front cab step, fireman's side only: use DA 1801 or DW 276 can antenna or short length of styrene rod or scrap runner
  • Air glad-hand connector immediately behind the above filter, both sides: cut short length from DA 1508
  • Replace jacking pads: CAN 2154
  • Replace handbrake tensioner: CAN 2152
  • Ground light, engineer's side only: DW 172 or OMI 9708
  • Rerail frogs: DW 119 for older "butterfly" type, OMI 9375 for the later type
  • Air filter & moisture trap: DW 139
  • Air pipes in/out of air reservoirs and filters: wire
  • Drain cock & moisture trap at rear end of air reservoirs: comes with CAN 2155, use very fine wire for drain line down along side of fuel tank
  • Traction motor cables where they show: DW 224 or wire
  • Trust plates on deck sill at rear: decal

    Fuel Tank

  • Add second, rear fuel filler: supplied
  • Breather up and down pipes at front of fuel tank: supplied
  • Drain bar, rear of fuel tank: supplied
  • Sump drain tank: supplied, BUT note that the drain hose goes straight down, it does NOT bend in and then down to run against the fuel tank.
  • Air box drain pipe, front and rear of fuel tank: supplied
  • Various additional drain pipes: use supplied or CAN 2156


  • Air lines to air cylinders: wire
  • Speed recorder: DA 2807 or DW 284
  • Sander brackets & lines: DW 330 plus fine insulated wire

  • Note that 5356-5373 were delivered with inboard sander lines, but they were removed at some point, leaving just the outboard sander lines, which will interfere with the steps.

    AL = A-Line (Walthers manufacturer number 116)
    CAN = Canon (191)
    DA = Details Associates (229)
    DW = Details West (235) PIA = Precision Investment Associates (PFM)
    OMI = Overland Models Inc
    RF = Railflyer Model Prototypes (631)

    More involved changes that could be made:

  • Change coupler plates (coupler pockets) If there is one thing that mars this model it is the overly wide coupler pocket, or coupler plate. Manufacturers insist on making the pocket wide enough to slip the entire coupler box through the opening, which is what makes it so grossly wide. The walls of the pocket itself are all that is needed to constrain the coupler.
  • Add the recess to the right of coupler plate While you're at It this should be easy enough to drill and file into the pilot and then back it up with a scrap of sheet styrene.
  • Move dynamic brake vent back On the model this rectangular vent is mounted on the rear portion of the dynamic brake insert, but it should be in the next roof panel back, a bit ahead of center.
  • If you really want to take it further you can replace the steps with see-through photo etched treads from Canon, and add safety tread deck plates from Canon or Railflyer.

  •     Detailing Athearn's Rio Grande SD40T-2 addenda
    Posted by: Jim Eager
    Date: Wed Nov 28, 2007 2:10 pm ((PST))

    After spending a couple hours looking at photos of the fuel tank area of the SD40T-2s, I think I have the various drain plumbing figured out.

    There is a small diagram at the bottom of the Athearn parts sheet that shows where some of the pipes go. The rear of the tank is at the left, the front of the tank is at the right. None of the pipes are numbered, not all pipes are shown, and the Grande Units did not use all of the pipes that are shown or supplied.

    Here are the ones to use:

    Front of fuel tank

    Rear of fuel tank That should about do it.

    Oh, the coupler lift bar on the rear pilot does NOT have the loop handles.

       Activating a Mars light effect in your new Tunnel Motors
    by Joe Snoy & Steve Orth

    Both Steve and I have activated a flashing Mars light effect in our Tunnel Motors (TMs). As delivered, Athearn's TMs have all the forward lights ganged together and activated by F0 (no flashing Mars). Here are 2 options for activating a Mars light on the nose of your TM. Steve implemented Option 1 (lights wired in parallel) and I implemented Option 2 (lights wired in series) with some help from Steve.

    Option 1 (Steve's method - light bulbs wired in parallel)

    Option 2 (Joe's method - light bulbs wired in series)

    Other installation variations are possible depending on the decoder you choose and the function key you want to use to activate the Mars light effect. The most tedious aspect of the installation is attaching one leg of the bulbs to the Blue decoder wire. Unlike the Green wire, the decoder Blue wire must remain connected to the circuit board to complete the headlight circuit.

    Steve's comments:
    The Digitrax Mars light effect will be better. The NCE flash rates and brightness are not programmable. Digitrax uses their memory to allow programming that stuff, but they have no memory allocated to hex-to-decimal conversion, thus the more difficult programming. NCE uses the memory for conversion. I like the Digitrax lighting effects, but I *hate* programming those things. I have one in a DRGW SD45. It does look good.

    I ran my 32 car hopper train with a SD40T-2 and a SD50 on the point, a SD40T-2 and a SD50 as the swing helper, and a SD40T-2 as a rear pusher. Pretty cool. That's Rio Grande railroading at its best!

    More MARS Notes
    Disconnect the nose lights from the light board. I'd change the wiring to connect the nose light bulbs in series. They are in parallel now. We do this so that if one burns out, both lights go out but the good bulb stays good. If you leave them in parallel and one goes out, the remaining bulb will see twice the current and will light *really* bright for a while, and then it will be forever dark.

    Solder an ~630 ohm resistor in series with the bulbs. I think the closest common resistor is a 610 ohm. That will be fine. Connect the bulb and resistor circuit to Output 1 on the decoder (Green wire). I don't think there's a connection on Athearn's light board, but I may be wrong. Probably worth checking on tonight.

    Program your decoder to put output 1 to a function key. I like to use F3 because F3 is not used by anything decent on sound decoders (usually the stupid sounding "coupler crash" that sounds more like some kind of dying animal). Program output 1 to be a Mars or Gyralight. They are different, but sometimes one looks better than the other.

    Don't attempt to use an LED for the Mars or Gyralight. LEDs do not turn on and off slowly. They tend to be full on or full off, and you need the dim-bright-dim-bright.... action for the simulation to look good.

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    This page last modified 3 December 2007.