Athearn SD45T-2 by Mike Acker

They're here, after months of waiting in anticipation; the Athearn SD45T-2 tunnel motors have arrived. The excitement created at the July National Model Railroading Association convention set up the anticipation for this release. Pre-orders for this locomotive at many hobby shops were at numbers unseen for any other model railroading release, with many multi-unit pre-orders included.

Why the excitement, especially for a locomotive that was originally purchased by only one railroad? Just look at it, this is the tunnel motor, the epitome of mountain railroading. It has that classic EMD Spartan cab with the exposed radiators mounted above the cooling fans and the large breather screens below. When you think tunnel motor, you can't help thinking of them heading up a long drag across Tehachapi, Cajon, or Donner. Sorry folks, but this is a West Coast thing.

It was during the late 1960s, in the quest for a new high horsepower, heavy hauling locomotive, the SP selected the EMD SD45. The SD45 offered the desired horsepower (3,600), and it was a familiar EMD platform for the maintenance crews. With the higher horsepower came the need for additional cooling of the prime mover, which resulted in the flared radiator design on the SD45. These flared radiators increase the ability to cool the prime mover. Soon after their delivery, problems started to develop with the SD45 overheating, particularly in the tunnels and snow sheds on Donner Pass.

Like most EMD locomotives prior and including the SD45, the radiator cooling air is drawn through filters mounted high up on the locomotive hood. Unfortunately the air near the ceiling in the tunnels would turn hot from exhaust gases from each locomotive that passes through. As the ceiling air degraded and increased in temperature, the cooling effects would degrade which led to overheating of the prime mover, and the subsequent locomotive shutdown would cause the whole train to stall. To solve this problem EMD and SP got together to come up with a solution. It was then that the concept of drawing cooler air from the tunnel floor was determined to be the answer. This meant, however, a lower air intake for the cooling fans was required. To test this theory, eight SD45 units were fitted with air intake shrouds that would channel air up from the walkway level to the intake filter screens. These modifications were referred to as "elephant ears" and the results proved to be very valuable.

The solution led to the redesign of the standard SD45 that resulted in a whole new locomotive model, The SD45T-2 tunnel motor. These were referred to as "tunnel motors" since this was their reason for the design. The frame for the SD45T-2 tunnel motor was extended out to 70-feet 8-inches from the 65-foot 9inch SD45 frame. This extension was to accommodate the extra long radiator and the 4,400-gallon fuel tank. The new tunnel motors utilized the same 20-cylinder, 3,600 horsepower 645E3 prime mover as the SD45. There were many physical and operational differences between these two locomotives. The most obvious change is the relocation of the radiator air intakes to just above the walkway.

This locomotive also came with all of the new Dash 2 features which includes the new HTC truck sideframes and upgraded electronics, just to name a few. The first deliveries of the new SD45T2 model took place in February of 1972 and expanded through eight separate orders, which concluded in July 1975. In all, a total of 248 SD45T-2 tunnel motors were delivered in two different roadnames under Southern Pacific; 84 went to the Cotton Belt (SSW) and the Southern Pacific (SP) received 164. The SD45T-2 is a pure SP locomotive, as no other railroads ordered any. Today you can find many of these locomotives on regional and shortlines as a result of retirements and purchases.

The other tunnel motor, the EMD SD40T 2 is very similar in appearance to the SD45T-2. The two simple ways to identify them from each other is that the SD40T-2 has a snoot nose and only 2 cooling fans under the radiator compared to 3 for the SD45T 2. How can you tell how many radiator fans are under there? Look below the radiator section and locate the rectangular access doors. These are the access doors for the radiator cooling fans. Thus, 2 doors equals 2 fans and 3 doors give you 3 fans. Let's take a look at the new Athearn model to see if it measures up to all the hype.

The Model

In this first release of the SD45T-2, Athearn offers them in three roadnumbers, plus an un-numbered version each for the Cotton Belt (SSW) and SouthernPacific (SP) as well as an undecorated early and late version. The decorated units reflect the early deliveries from EMD, with the late style undecorated an odd ball in this release. Later this year Athearn plans a second release with SP Kodachrome, SP Speed lettering, KCS, and Bessemer & Lake Erie. This next release does not include any late versions of this locomotive.

This locomotive comes in the typical Ready-to-Run locomotive packaging and in the box it looks pretty impressive. Taking one out of the box is when you come to the conclusion that Athearn definitely did their homework on this one. From front to back and top to bottom, this is one impressive locomotive model. The lettering, data, and safety placards are sharp and right on. The paint pigment looks good, and it is applied evenly with excellent separation between the scarlet red and gray. All of the builder's plates, warnings, and information stencils are accurate and placed correctly. The front pilots of the SSW units have the proper number placement. Even the truck sideframe stencils are right on.

A real close look at the locomotive reveals that the version specific details were included accurately. Some good examples of this are: The snubber bracket mount on the center journal of the sideframes is the type found on the early versions. Other examples include the bolted shut battery boxes, number of cab vents, front cab louvers, cast frame jacking pads, and the side mounted round dial fuel tank gauges. The configurations of the snowplows are correct too, with one on each end for the SP unit, as opposed to the SSW unit only having a forward plow and a MU cable tray on the rear. The tooling on this shell is nothing short of excellent. The walkways feature nicely done diamond treading, while the door latches and louvers are fine and crisp. The steps leading to the cab doors are of the etched, see-through variety. On the top of the long hood, the exhaust stack and cooling fans are of the Cannon and Company type see-through quality.

There are loads of factory added details to these locomotives. I didn't realize how many detail parts were added until I examined an undecorated model. I found the details to be very fine and accurate. The grab irons applied at the factory are of the thin wire type, as are the grabs above the radiator. These radiator grabs are also very delicate, so be careful you don't touch them. The best of all factory added details is the radiator air intake screens. This looks really good and has that prototypically correct seethrough look. The only thing that may not be prototypically correct is the truck gear tower visible through these screens. I guess if this bothers you, you can always modify it so that the motor only drives the front truck.

The cab is pretty impressive too, with side windows that can be opened and closed. The remaining cab windows are flush fitting and include the prototypically correct L-shaped window. The top of the cab is well detailed with a brass air horn, whip antenna, and the bell positioned properly. The bell has a nice touch with a brass wire attached to its top. You'll need to also be careful of this detail, as it is also very small and breakable. On the flip side, there are a few negative things that I feel that are worth mentioning.

First are some details that were left off. These are easy items to add if you feel the need. These parts include; the uncoupler levers, eyebolts, MU hoses, air reservoir lines, air filters, brake cylinder lines, and windshield wipers. They make it easy though, the locations for the eyebolts are already marked on top of the long hood with dimples. The snowplows used on both samples are smaller than the prototype and are missing MU doors. The last discrepancy worth pointing out is the use of the light bulb ends for headlight lenses instead of mounting them behind actual lenses.


On the track, the new tunnel motors performed relatively well. I found that the SSW locomotive performed better than the SP unit. It appears that the gearing in the trucks of the SP unit may have been binding a little. This problem didn't keep the locomotive from performing satisfactorily. It may require a little tinkering to get it to run better.

Under the hood, you'll find the traditional Athearn flywheel drive system with the exception of the Ready-to-Roll drive couplings upgrade. New to this line is the improved chassis with its added weight. This additional weight to the chassis brings the total locomotive weight up to nearly a pound and a half. Because of this added weight, the starting voltage for both sample units was relatively high. Some of the voltage consumed can be attributed to the four front light bulbs.

At the lower speeds, the locomotive samples both ran a bit rough with difficulty maintaining a constant speed. At the medium to high-speed range, this locomotive can pull with the best. The top speed of the locomotive is comparable to the prototype. A slight setback with the locomotive performance is that the headlights don't illuminate until the locomotive reaches medium speed (7 volts). The DCC decoder installed in the locomotives was an NCE D13SRJ. Removing the shell from the chassis takes a little more work than prior Ready-To-Run locomotives. In the past, the disassembly of the shell and chassis was to remove the coupler and pockets, but things have been changed. Athearn has added two screws that directly attach the chassis to the shell. There is one screw underneath each of the trucks on the fuel tank ends. Once the shell is removed, the decoder installation is very simple operation of unplugging the little directional jumper board and plugging in the new decoder.

Back on the track with the new decoder, I found that the tunnel motors performed much better. Through the entire speed range the locomotives performed consistently. The start voltage may be much higher than most model locomotives, but that is the nature of this beast. With a little playing around with the DCC settings (i.e. start voltage, motor kick voltage, acceleration, etc.), the performance of this locomotive can be improved immensely.


Was all this hype and anticipation for the new SD45T-2 tunnel motors able to meet my expectations? You bet it did. From the quality paint and stencil work to the fine details, these locomotives look great. Athearn nailed this one right on the head and has upped the ante for fine, detailed locomotives to come. The drive system maybe a weak point but that can be remedied by a DCC decoder and some configuration magic. Athearn didn't just meet my fussy expectations, but actually exceeded it. Count me in for a few more tunnels.