Rivet Counter N Scale EMD GP40 Phase Ia3, Milwaukee Road/1960s-1970s Era

In May of 1965, a strange new locomotive model would roll out of the EMD’s La Grange (McCook), Illinois locomotive plant. Clad in black, this new 4-axle unit simply wore the number “433A” on its cab sides and number boards. From the walkway on down, it resembled a late-production GP35, with a thinner sill at the midsection, and a deeper fuel tank, but above the walkways, one could tell this was something different.

While the equipment layout resembled that of a GP35, the radiators at the end of the locomotive were unlike anything else in the EMD lineup, featuring three 48” radiator fans instead of the dual 48” and single 36” arrangement of the GP35. Moreover, the new model featured flared radiator intakes, hinting at deeper radiator cores to dissipate the heat from increased horsepower output. This new locomotive, the GP40X (not to be confused with the GP50 testbed model of the same name introduced in 1977), was a harbinger of things to come: the GP40.

From the technology tested on the 433A, the GP40 was formally introduced in late 1965, with an order of 50 units for New York Central. The GP40 was designed with lessons learned from its predecessor, the GP35. Among them was an improved electrical control cabinet, designed for more reliable operation and ease of maintenance compared to the complex control scheme of the GP35. Built on a longer frame than the GP35, the GP40 could be optioned for a fuel tank capacity of up to 3,600 gallons. Most importantly, the GP40 introduced a new prime mover series for EMD: the 645.

With the previous 567-series having reached its practical limits for horsepower output, the 645 series would reduce overall stresses on the prime mover thanks to a larger cylinder bore (645 referring to the displacement of each cylinder) and allow for higher horsepower output, and would go on to become one of their most popular prime mover designs in all of railroading. The GP40 would feature a turbocharged 16-cylinder variant of the 645, producing 3,000hp, making the new locomotive model suitable for all types of service. 

The GP40 would quickly prove to be popular with the railroads of the day, with over 1,200 built before production ended in 1971. With its relatively high-power output spread over four axles, allowing for quick acceleration, GP40s would prove to be useful on relatively light, high-speed trains, such as the early intermodal trains of the era. Penn Central (PC) would wind up as the largest original GP40 owner, acquiring 170 units over multiple orders. Despite the eastern road’s struggles, consists of black GP40s could be found all over the system handling all kinds of freight, eventually trading their somber black paint for bright Conrail blue. 

Another major owner was the Baltimore & Ohio, who was just behind PC with a grand total of 161 units purchased. These units, along with GP40s purchased by future merger partners Atlanta & West Point; Chesapeake & Ohio; Georgia Group; Louisville & Nashville; Richmond, Fredericksburg, & Potomac; Seaboard Air Line; Seaboard Coast Line; and Western Maryland, would eventually be distilled down to eastern giant CSX, which ultimately resulted in a huge palette of GP40 paint schemes and variety under one roof.

Out west, the GP40 found a ready buyer in the Denver & Rio Grande Western, who bought a total of 43 units, with their 1969 delivery, D&RGW 3081-3085, being distinctive in being their first factory new units delivered in the flying Rio Grande “billboard” lettering scheme. They joined the road’s other 4-axle road units in service at the time, including GP30s and GP35s, in all kinds of service. They could be found locking couplers with the 6-axle units in the road’s fleet working coal drags, all the way to hot intermodal trains. 

Western Pacific Railroad would acquire a sizable fleet of 44 units, with initial orders sporting large Pyle-National “barrel” headlights front and rear, along with their attractive orange and silver “Zephyr” paint scheme. Later deliveries would do away with that bright livery in favor of the “Perlman” scheme of dark green with orange chevron striping front and rear. These units would settle into a routine on the “Wobbly” alongside the rest of the roads’ fleet, which was exclusively 4-axle, before joining merger partner Union Pacific’s roster in 1982.

Santa Fe would take the title of “hard luck” GP40 owner, acquiring a single unit, TP&W 1000, through 1983 merger partner Toledo, Peoria, & Western, which itself was a former EMD “loaner” unit #21 that originally spent time on the Penn Central. After formally joining the AT&SF roster in 1984, the lone GP40, renumbered to AT&SF 2964 and repainted into their blue and yellow bonnet scheme, operated alongside Santa Fe’s other 4-axle units, but was destroyed in a wreck in 1988, lasting only a scant four years as a Santa Fe unit. 

Overall, the GP40 would be a popular model for the builder, with many units sold new and lasting throughout the lives of their original owners, and in many cases, into their successors. As they lived through the typical depreciation cycle, many would be retired and sold off to new owners by the 1980s-90s. Rebuild programs would also find many cast-off GP40s finding new life for new owners, being overhauled and in many cases, having upgrades, such as Dash-2 (or equivalent) electrical systems, installed to improve their reliability and performance.

Southern Pacific, which skipped the GP40 altogether (aside from 8 purchased new by its subsidiary Cotton Belt), would amass a sizable fleet of rebuilt GP40s via rebuilder Morrison-Knudsen, designated GP40M-2, that appeared in the early 1990s. Coming from a variety of original owners, these rebuilt units were a needed shot in the arm for the power-short railroad. Chicago & North Western was another railroad that took advantage of “cheap” secondhand GP40s, acquiring a number of former NYC/PC/CR GP40s in the mid-80s for all types of service on the road.

Another popular rebuild option was to use a GP40 core unit as a basis for a 2,000hp “GP38” conversion, eliminating the expensive turbocharger in favor of an easier to maintain Roots-blower combustion air arrangement. Some of these rebuilds saw one of the radiator fans removed and blanked out… cooling needs were reduced, thanks to the lower H.P. rating… as well as a boxy paper air filter housing added to the front of the engine compartment roofline. 

The single large turbocharger exhaust would be replaced with a pair of “straight” exhaust stacks, with the end result being a relatively inexpensive to maintain, intermediate-horsepower locomotive suitable for all kinds of work. Roads like Union Pacific, which didn’t purchase GP40s new, was one of many customers for this type of rebuilt secondhand unit.

While GP40s on the mainline are a rare sight today, many are still out there putting in a solid day’s work, either for successor railroads such as BNSF and UP, or for the many shortlines and regionals that snapped up secondhand GP40s, in either original or rebuilt configurations. From the humble beginnings of a somber all-black demo, came one of EMD’s most popular 4-axle designs.