The EMD (Electro-Motive Division) SD40T-2 is a type of high-powered, six-axle, 3,000hp diesel locomotive built specially for the Southern Pacific and Rio Grande (DRGW) railroads from 1974 to 1980.
SP SD40T-2

An example of an SP (Southern Pacific) SD40T-2.

Although a modified version of the SD40-2 (as stated in an EMD owners manual), it initially inspired the current split-cooling designs for modern high-horsepower diesel locomotive technology throughout North America because of its once-experimental, yet revolutionary cooling or coolant system known as a "tunnel motor": which consisted of large air intake vents placed on the sides of the overall body or along the rear carbody of the actual locomotive accompanied by angled louvers or vents on top of the rear hood, and was used for cooling the engine or prime-mover by releasing heat and releasing emissions from the engine compartments while traveling through tunnels up steep mountain grades.

Many still exist, but are no longer owned, used, or seen on the Union Pacific as of 2009 (the only major, Class 1 owner which owned a large fleet as a result of the acquirement of the SP and D&RGW in 1996). The remaining units were officially retired from the company's roster in 2010 (including the sole-surviving unpatched D&RGW SD40T-2 unit: #5371).

Many currently operate on various shortlines and leasing companies (including rebuilt and non-rebuilt SD45T-2 units; which were rebuilt as a result of engine issues like its predecessors) while one (DRGW #5371) is preserved, and currently resides at the Utah Railway Museum in Ogden, UT.


During the 1970's, six-axle diesel locomotives were in high demand on various Class 1 railroads throughout the United States, and the most desperate of them all, were the Southern Pacific (aside from the SSW subsidiary of the SP) and Rio Grande, who began to wear their aging four-axle diesels for mainline service and were in desire need of stronger and more powerful six-axle diesel locomotives that wouldn't overheat so easily going up-grade at full throttle or Notch 8 like the original SD40-2 and subsequent SD45-2. Hence, EMD's solution was by inventing a revolutionary and advanced cooling system equipped on an actual SD40-2 unit known as a "tunnel motor", which was able to be utilized whilst traveling up-grade through tunnels without ever having to worry or fear hot air being drafted or sucked back into the locomotive like with the usual top-mounted air intakes on models like the original SD40-2. Thus, the creation of the EMD SD40T-2 (the "T" meaning "tunnel motor"), which helped solve previous issues that plagued diesels traveling up-grade through the steep mountain routes as-seen on routes like the DRGW's Tennessee Pass and the SP's Donner Pass.
D&RGW tunnel motor with an SP tunnel motor and ATSF Dash 7

A DRGW SD40T-2 with an SP SD40T-2.

Henceforth, the SD40T-2 became an initial success, yet only the SP and DRGW ordered SD40T-2 and subsequent SD45T-2 units for use as helpers and/or units employed in general revenue service.

The SD40T-2 survived well past the 1996 merger of the UP and SP until 2009. Though, many SD40T-2 units left retaining their original liveries still exist as of today (yet, most of said former SP and DRGW-painted units are commonly seen in scrap yards and on shortlines; including those repainted into UP paint). Many have since been rebuilt or auctioned to shortlines or exported for use in Latin America.


There is often a confusion between the SD40T-2 and SD45T-2.

An SSW SD45T-2 (notice how long it is compared to its counter-part, and the presence of three hatch doors versus two on the radiator section).

The main differences between distinguishing the SD40T-2 and SD45T-2 apart from one another, is by the hood, frame, the amount of fan doors (SD45T-2 having 3 to 4; SD40T-2 having 2), and the actual length of both models (SD45T-2 being slightly longer due to having a larger, 20-cylinder engine compared to the 16-cylinder SD40T-2).


  • The SD40T-2's proof of being a modified version of the SD40-2 is by the EMD owner's manual statement. Yet the prototypes actually were completely different from the final product with having a completely different turbocharger placement due to the cooling or coolant system's placement (making the turbo blower duct used for the tunnel motor as opposed having been used for the actual turbocharger).
  • DFTR #2003 is a former SP SD45T-2 fitted with an EMD "safety cab" or "wide-cab" used for crash test experiments for Operation Lifesaver and various other safety companies.
  • SSW #9389; an SD40T-2 from the SSW portion of SP's; roster was painted in an exclusive bicentennial scheme in 1976 to commemorate the 200th Anniversary of the United States government.
  • The Bessemer And Lake Erie shortline railroad (owned by CN as of 2008-2009) owns a fairly large fleet of rebuilt SD40T-3 units which are rebuilt from various SD45T-2 and SD40T-2 units once owned by the SP.
  • Six former DRGW SD40T-2 units were exported to Brazil to serve the newly-established FCA (Ferrovia Centro-Atlantica) railway in Brazil. These units are rebuilt to navigate the steep routes in the various Brazilian mountain ranges where standard-gauge tracks are deemed to be too wide. Such units were rebuilt with longer frames, narrow-gauge "B-type" trucks (in a combined B+B-B+B configuration) and rebuilt dynamic brake grids.
  • Several SD40T-2 and SD45T-2 units were also exported and eventually rebuilt for the ALL (America Latina Logistica) logistics company as well. Though, such units are rebuilt in a much different manner (see below).