The following article was written by contributing author Jonathon Leese.
The year is 1966, and Electro-Motive Division of General Motors (EMD) is top dog in the locomotive sales world. With very few exceptions, the tens of thousands of EMD-built diesel electric locomotives had snuffed out the fires of the nation’s last steam locomotives for good a mere 6 years prior. Barely 20 years earlier, diesel-powered locomotives were nothing more than a curiosity, and now they were here to stay. All was well for EMD, however the railroads now came to their preferred builder with a new problem: the locomotives that had replaced steam, some now nearing 20+ years of age, were worn out and in need of replacements. For the first time, EMD now had to build a locomotive that would be replacing one they had already built. Increasing competition from General Electric (GE), while still barely making a dent in EMD’s market share, were also raising more than a few eyebrows. The pressure was on for EMD to deliver a home run.
As the 1960s dawned, so too did the race for more horsepower. While early diesel locomotives were more efficient and cheaper to operate than steam, it often took 2 or more of them to equal the power and or speed of a large, modern steam locomotive. EMD had been long content to build normally aspirated locomotives in their F, E, GP, SD and SW series, all of which used a variant of their trusty 567 engine. However, 1,800 horsepower was about all that could reliably be mustered from the 567, even in its 16-cylinder form. Union Pacific, a railroad with a long-standing reputation for always wanting the biggest and best motive power to move their trains, began experimenting with turbocharging a small group of their GP9 fleet. These upgraded GP9s, later dubbed “Omaha GP20s” marked the first successful implementation of turbocharging a 567 engine for railroad use. Though EMD had been experimenting with turbocharging since 1955, they had never offered a turbocharged engine in a locomotive. At the urging of Union Pacific, EMD began developing their own line of locomotives using turbocharged 567 engines, dubbed the 567D3.
The first EMD turbocharged locomotive to be cataloged was the 4 axle GP20, which used a 16-567D3 rated at 2,000 horsepower. A couple of years later their first 6 axle turbocharged locomotive, the 2,400 HP SD24, was introduced. These were subsequently followed by the GP30 (2,250 HP), GP35 (2,500 HP) and SD35 (2,500 HP). By this point, the 567 engine had reached the end of its practical life for further development. Both the GP35 and SD35 experienced problems in the field as a result of too much power being squeezed out of the 567D3. Concurrently, the limits of traditional diesel locomotive wiring were being reached as well. Diesel electric locomotives employ a transition system to prevent overloading the traction motors and “cooking” their wiring. Without getting into too much detail, it is basically the electrical equivalent of changing gears, in which the power being generated by the generator shifts from series to parallel. By the time the GP35/SD35 were introduced, the transitions needed were complex and many. The GP35/SD35 transitioned a total of 16 times depending on variables like how hard the locomotive was working and how fast it was going! In addition to being complex to work on and troubleshoot, the locomotive would also cease to load while transitioning, basically rendering it useless for however long it took for the transition to take place. This problem was even further compounded when railroads would run sets of multiple GP35s, SD35s, or similar older models together. 4 GP35s together would transition separately a total of 64 times! This was another issue that EMD was looking to address.
In 1965, GE introduced their first 2,800 HP U28C, and American Locomotive Company (Alco) introduced their 3,000 HP C630. While these locomotives did not represent a serious threat to EMD, it did leave them behind in horsepower race. By 1966, EMD was ready. Enter the 645 (645 cubic inches of displacement) engine, an all-new diesel engine incorporating many successful design aspects of the 567 and building upon them. The engine was cataloged in 8, 12, 16- and 20-cylinder varieties for North American railroad use, and was also offered both as a normally aspirated “Roots blown” version and a turbocharged version. Each engine came paired with its own locomotive model: the SW1000 (1,000 HP 8-645E), SW1500 (1,500 HP 12-645E), GP38/SD38 (2,000 HP 16-645E), GP39/SD39 (2,300 HP 12-645E3), GP40/SD40 (3,000 HP 16-645E3) and SD45 (3,600 HP 20-645E3). With this new line of locomotives and diesel engines, EMD now had a model to suit virtually any railroad’s specific needs. Gone were the 16 transitions of the 567-powered 35 series line, the new 645-line locomotives transitioned only once. Parts and electrical components were simplified as well, with all variations of the 645 using the same parts, and every locomotive using the same type of generator, among other things. Many models shared frames and trucks as well, with the GP38, GP39 and GP40 all using the same frame. The same was true for the SD38, SD39 and SD40. This commonality of components and subsystems between multiple locomotive models reduced costs and increased parts interchangeability and simplified training for the railroad personal that maintained them. Indeed, the introduction of the wonderfully simplified 645 series locomotives put many older and cantankerous Baldwin, Fairbanks Morse, Alco and even EMD locomotives out to pasture for the final time. The 645 line began what enthusiasts now refer to as the “second generation” of diesel electric locomotive development.
The new locomotives were a big hit, with the 3,600 HP SD45 being the best seller with 1,260 units produced by the time production ceased. The SD45 was not only EMD’s first production locomotive to surpass the 3,000 HP mark, but also their first to use a 20-cylinder engine as well. Because of the larger engine, more cooling was needed, which led EMD to design the unique angled “flared radiators”, a major spotting feature of the SD45. The first SD45 delivered was Great Northern Railway #400, which the railway dubbed “Hustle Muscle” for its ability to move long, heavy freight trains at higher speeds than older models. Often an SD45 was considered a 2 for 1 replacement on trains compared to older EMD models like the 1,500 HP F7 or 1,750P GP9. Unfortunately, the SD45’s time in the spotlight was relatively brief. Early on in their careers, SD45s were plagued with teething problems, the biggest of which was their tendency to destroy their crankshafts due to the flexing of the engine block at higher RPMs. Being 20-cylinder models, they also consumed more fuel than their little brothers, the 3,000 HP SD40, especially at idle. EMD soon corrected these crankshaft failures by strengthening the block of the 20-645E3, but by then their reputations had been tarnished beyond redemption. The initial reliability problems, increased fuel consumption, and extra cost compared to less powerful models was not deemed worth it for most railroads. Subsequently, SD45 sales stalled while railroads began purchasing other EMD models instead.
EMD also produced a trio of interesting SD45 variants, the SDP45, FP45 and F45. The SDP45 was a lengthened SD45, the extra space being (at the rear of the locomotive) utilized to house a steam generator, which was needed to provide heat and power to North American passenger trains at the time. Railroads at the time were looking replace aging E and F unit locomotives in passenger service but were hesitant to do so because of how much money they were losing on passenger operations. It was also still uncertain at the time as to whether the US government would intervene and relieve the freight railroads of passenger operations. EMD offered an attractive solution; a more-or-less off the shelf freight locomotive with a steam generator that was geared for passenger operation. If passenger operations ceased, the locomotives could be easily regeared for freight service. The Southern Pacific and Great Northern bought their SDP45s (10 and 8, respectively) for passenger service, but the Erie Lackawanna also signed for 34. These were SD45s with SDP45 bodies, but they were not equipped with steam generators and technically designated SD45Ms. EL’s reasoning for their purchase was the longer body could hold a longer fuel tank, allowing for increased range between refueling.
The famous Atchison, Topeka & Santa Fe was also in the market for new passenger locomotives, but like other railroads were hesitant to invest in a strictly passenger-dedicated locomotive at a time when the future of the American passenger train was in doubt. However, Santa Fe still took a lot of pride in their passenger trains and public image and went to EMD wanting a locomotive that looked like a passenger locomotive, not a freight model. EMD’s solution was the FP45, an SDP45 with a fully enclosed, semi-streamlined, cowled car body. The Santa Fe bought 9, and the Milwaukee Road also purchased 5. While not as streamlined as the E and F units of the past, the FP45 design was still attractive and they were regarded as very handsome locomotives compared to their freight contemporaries. EMD also marketed a freight version of the FP45, dubbed the F45, which lacked a steam generator and rode on a standard SD45 frame. The Santa Fe bought 40, 20 of which were equipped with pass through steam lines and geared for passenger speeds so they could be used in passenger service in conjunction with the FP45s and older passenger models. Great Northern and successor Burlington Northern also bought a combined total of 46 F45s, with the intent of having one in the lead position on most of their freight trains in the winter months. The thinking was that the cowl car body would offer better protection for train crew and maintenance personnel in the cold weather but having an F45 lead every train soon proved to be logistically impractical.
The introduction of the new line of locomotives also marked the first time that the 6 axle models outsold the 4 axle versions. Trains were getting longer and heavier, and 6 axles had more tractive effort than the smaller 4 axles. As the SD45’s popularity waned, railroads turned to EMD’s next most powerful model, the 3,000 HP SD40. Using the 16-645E3 turbocharged engine, the SD40 represented the first truly versatile 6 axle locomotive. Here was a locomotive that was equally at home hauling a fast mail train, medium speed mixed freight, low speed drag, or switching in a yard, and had the power and flexibility to do any of it with ease. The 3,000 HP 6 axle locomotive would become the standard of the industry for the next 20+ years. They represented the perfect compromise in size, horsepower, tractive effort and fuel efficiency. By the time SD40 production ceased, over 1,000 were built for the North American market. Like the SDP45, a steam generator equipped SDP40 variant was also built in small numbers for railroads desiring new passenger power that could be utilized in freight service later. EMD also cataloged the less powerful SD39, which used the 2,300 HP turbocharged 12-645E3 and was introduced a few years later in 1968. Compared to the SD40, the SD39 was a sales flop, with just 54 units built. The 2,000 HP SD38, which utilized the roots blown 16-645E engine, was only slightly more successful, with about 70 units built. It was hard to compete with the versatility of the SD40. The SD39 and SD38 found more favor in specialized uses like drag freight service and hump yard switching, because of their higher tractive effort at lower speeds. Horsepower was also not as much of a concern in low speed applications.
While the 6 axle models attracted lots of attention, the 4 axle models established what were to become (and still are) the standards for medium duty freight locomotives: the GP40 and GP38. Each was a lighter, 4 axle version of their SD40 and SD38 cousins. The GP40’s 3,000 HP and more modest tractive effort was best suited for higher speed freight service, and most of the railroads that bought them used them for just that. Trios of GP40s would often replace quartets or quintets of older EMDs like F7s and GP9s on priority freight trains. While their tractive effort was roughly equal to that of the less powerful GP38, many engineers found the higher horsepower GP40 to be slippery at lower speeds under a heavy load. It was because of this, and the fact some railroads were not interested in turbocharged locomotives, that the Roots-blown 2,000 HP GP38 also proved to be very popular. The GP38 was much like the SD40: equally at home in almost any kind of service. In their heydays, GP38s handled virtually everything from lowly local freights to the hottest mail trains. They became the spiritual successor to EMD’s versatile GP7 that had debuted some 20 years earlier. All in all, both models were very successful, with over 700 GP38s built and nearly 1,200 GP40s. A later production variant of the GP38 was the GP38AC. Instead of a DC generator, the GP38AC used an AR10 alternator that would become standard on later EMD models. 261 GP38ACs were built between 1970 and 1971. The 2,300 HP GP39 was also offered but found few takers. Chesapeake & Ohio had the largest fleet with just 20 units of the 23 built.
GPs and SDs are fine locomotives for switching cars in yards, but the practice of using such large units in such a diminutive role could be likened to using a Ferrari to tow a boat: it’s possible, but there are better tools to do the job. For switching, EMD fielded the 1,000 HP SW1000 and 1,500 HP SW1500. While they had abandoned the practice of horsepower model numbers with the GPs and SDs, the SWs were still classified based on horsepower. Switching locomotives are designed for maximum pulling power at low speeds, as they load very quickly. Many of EMD’s first production locomotives were switchers, and by the 1960s some of these were approaching 30 years of age, making them ripe for replacement. The 1,000 HP SW1000 was the least popular of the two, with 114 units built, mostly for private companies who needed their own on-site switcher. The SW1500 was almost identical to the SW1000, the main difference being a pair of exhaust stacks for the 12-645E on the SW1500 compared to one on the 8-cylinder SW1000. The SW1500 proved to be much more popular, with over 800 built. Unlike the SW1000, the SW1500 found favor with the larger railroads, with Southern Pacific having the most (208 units). Two variations of the SW1000 and SW1500 were also produced, the SW1001 and the SW1504. The SW1001 was an SW1000 with a lower profile cab for tight clearances more commonly found in industrial settings, while SW1504 was an SW1500 which rode on EMD’s Blomberg 4 axle truck (most SWs had either standard AAR type A trucks or EMD’s flexicoil truck) and was 2 feet longer than a standard SW1500 to accommodate them. The SW1504s represented some of the final SWs built, as EMD soon replaced them with the larger MP15 series in the 1970s.
Simply put, EMD had a home run with the 645 line. The railroads loved their improved reliability and ease of maintenance, and sales reflected this. GE began to fall even further behind EMD in sales, and Alco finally exited the locomotive market in 1970. As the 1970s dawned, EMD looked to improve upon their successful lineup of locomotives. The railroads were consulted, and the most requested improvement was even more ease of maintenance. Rather than design completely new locomotives from the ground up, EMD took their 645 series and tweaked them to near perfection. The new line debuted in 1972 and was known as the “Dash 2” line, or “version 2”. The GP and SD models remained the same, but now had a “-2” designation. A GP38 was now a GP38-2, an SD40 an SD40-2, and so on. The biggest difference between a Dash 2 locomotive and its predecessor was the electrical system. The Dash 2 line featured a simplified, modular electrical system, with large cards that could be quickly replaced if needed. Every Dash 2 locomotive used the same cards, so parts supplies were simplified. EMD had been experimenting with the technology since the late 1960s, and the massive twin-engine DDA40Xs built in 1969 for the Union Pacific marked their first application in a production locomotive. The final major improvement was the introduction of a new 6 axle truck, which EMD called the HTC truck. It offered better adhesion and a smoother ride compared to the flexicoil trucks that the SD38, SD39, SD40 and SD45 rode on. Indeed, the Dash 2 line proved to be even more popular than their predecessors, with production of some models spanning over 15 years.
While the SD45 had been the favorite of railroads the first go around, the improved SD45-2 failed to attract many buyers. Railroads still had a bad taste in their mouths from the SD45, and 3,600 HP was not as appealing as it once was, with 3,000 becoming the norm. While all the problems that plagued the SD45 had been resolved, the damage had been done. Just 136 SD45-2s were built, the bulk of which were for Santa Fe who stayed committed to 20-cylinder locomotives longer than most other railroads. While the SD45 had used a longer frame than the SD38, SD39 and SD40, the SD45-2 shared a common frame with the SD38-2 and SD40-2 (an SD39-2 was cataloged, but never built) which further simplified construction. No SD45-2s were ordered or built after 1974, giving the model a very short production run.
A variant of the SD45-2 proved to be a bit more popular, the SD45T-2. Nicknamed “Tunnel Motors”, the SD45T-2 featured air intakes at lower position on the locomotive body than the standard SD45-2. The model was designed at the behest of Southern Pacific, who desired a locomotive that would not overheat in its many miles of tunnels. Conventional EMD locomotives drew in fresh air for cooling via air intakes mounted towards the top of the rear of the locomotive’s long hood end. In long tunnels, the hot exhaust gases from locomotives working at or near full throttle at slow speeds for miles on end would be sucked in by the air intakes, causing them to overheat. The solution was to lower the air intakes to walkway level, allowing them to draw in cooler air from closer to ground level. The units performed perfectly, and Southern Pacific ordered 163 SD45T-2s along with another 84 for their Cotton Belt subsidiary.
The SD40 had laid the groundwork for what was to become EMD’s second best-selling model of all time, the SD40-2. Only the fabled GP9 had sold more units at that point in time. The SD40-2 used the 16-645E3 engine delivering 3,000 HP. Now paired with the Dash 2 electronics, the SD40-2 was more reliable than ever, immediately becoming the industry standard locomotive for the next 30+ years, and in many ways still is to this day. Like the SD40, the SD40-2 was equally at home hustling fast freights, lugging low-speed coal drags, or doing anything in between. By the time North American production ceased in 1988, EMD (and their Canadian subsidiary GMD) had delivered nearly 4,000 of them, including specialized variants. Many railroads ordered them by the hundreds, with Burlington Northern amassing a fleet of over 800, Union Pacific with over 600, and Canadian Pacific with nearly 500.
Variants of the SD40-2 included the SD40T-2, SD40-2W, SD40-2F, SDP40F, and F40C. The SD40T-2 implemented the same air intake design as the successful “Tunnel Motor” SD45T-2 and was also ordered by the Southern Pacific (229), Cotton Belt (10) and attracted a new buyer in the form of the Rio Grande (73). The SD40-2W was built by Canadian GMD for the Canadian National and featured a wider nose than standard EMD/GMD designs. Dubbed the “comfort cab”, the design featured a full-width nose with the front door mounted on the nose as opposed to on the front of the cab face. Designed to provide better crew comfort and increase safety in the event of a crash, the design would later be adapted by both EMD and GE in the late 1980s, becoming standard on most locomotives today. GMD built 123, all for the CN. The final freight variant was the SD40-2F, which essentially an SD40-2 with a fully enclosed, cowled car body for operation in cold and extreme weather conditions. Interestingly enough, when GMD built the SD40-2F (25 of them) for Canadian Pacific in 1988, regular SD40-2 production had ceased almost 4 years earlier, and EMD was busy producing their 60 series line of locomotives. Canadian Pacific wasn’t interested in SD60s however, they wanted more SD40-2s. Unfortunately, the SD40-2Fs suffered from several reliability issues, so much so that CP shied away from EMD products almost entirely for the next 25 years.
Reliability issues also plagued the passenger service SDP40F. Basically a cowl car bodied SD40-2 equipped with a steam generator, the SDP40F was built exclusively for Amtrak, and was their first series of locomotives bought new since their 1971 inception. It used the 16-645E3 and had a pair of steam generators. Unfortunately, the SDP40F was not a successful locomotive. The new HTC truck, which had been successful on the SD40-2 and SD45-2, was blamed for a series of derailments involving SDP40Fs at higher speeds. While it was eventually concluded that the trucks were not the culprit, many railroads slapped speed restrictions on Amtrak’s units, rendering their newest motive power basically useless. Orders for more SDP40Fs were canceled, and Amtrak focused on 4 axle locomotives from that point on. The SDP40Fs that weren’t traded back to EMD or scrapped (18 of them) were eventually sold to the Santa Fe, who re-geared and subsequently used them for years in freight service without incident.
Another interesting passenger locomotive, derived from the SD40-2 and SDP40F, was the F40C. Riding on the same frame and trucks as the SD40-2, the F40C was slightly shorter than the SDP40F due to the fact that the F40C was equipped with a head end power generator rather than steam generators. It’s 16-645E3 engine was rated a slightly higher 3,200 HP, with the extra power going to the HEP generator. In a way, the F40C was a kind of stepping stone between the flawed SDP40F and the very successful 4 axle F40PH. EMD built 15 of them for Chicago’s Rail Transit Authority in 1974, and they were the last 6 axle passenger locomotives EMD built for the North American market until the mid-2000s. Visually similar to the earlier FP45, F45 and SDP40F, the F40C’s most distinctive feature was their fluted stainless steel side panels, which were requested by RTA so the locomotives would better match the stainless steel commuter cars they were to pull.
The successor to the SD38, the SD38-2, sold a bit better than its older brother, with just under 100 built before production ceased in 1979. Like the SD38, it used the 16-645E normally aspirated engine rated at 2,000 HP. The SD38-2 found favor with heavy haul and terminal railroads like the Bessemer & Lake Erie and Elgin, Joliet & Eastern, where tractive effort was a much greater concern than speed. In recent times, several SD40-2s have had their turbochargers removed and have been rebuilt to SD38-2 specs and HP. EMD also cataloged an SD39-2, as mentioned earlier, which would have used the turbocharged 12-645E3, but never received an order for one.
On the 4-axle front, EMD fielded the new and improved GP38-2, GP39-2 and GP40-2. Unlike the original 40 series, the GP38-2 proved to be the more popular model this time around. Like the SD40-2, the GP38-2 performed equally well in all kinds of service. Reliability was better than that of even the GP38, and the railroads took notice, with nearly 2,300 GP38-2s being built before production ended in 1986. GMD also built the GP38-2W, equipped with the Canadian “comfort cab”, for the Canadian National. The GP38-2 proved to be quite popular just about everywhere, with almost every major North American railroad (along with a myriad of smaller ones) owning at least a few. Much like the SD40-2, the GP38-2 became the standard locomotive for medium and light duty applications, a title which still holds true even today.
The next most popular 4 axle was the 3,000 HP GP40-2. While the railroads still were starting to prefer high horsepower 6 axle models over 4 axles, EMD still cranked out nearly 1,200 GP40-2s over the course of production. Like their GP40 cousins, the GP40-2s were more slippery at lower speeds under heavy load but were right at home on higher speed freight trains. Railroads like Conrail and Southern Pacific fielded fleets of GP40-2s on high priority merchandise trains. Chessie System bucked the trend of favoring the SD40-2 over the GP40-2 and had the largest fleet, with 348 GP40-2s spread across their Baltimore & Ohio, Chesapeake & Ohio and Western Maryland subsidiaries. They became the go “anywhere, do anything” locomotive for Chessie, and one could find them in just about any kind of service wearing their bright disco-esque paint scheme. In Canada, GMD built the comfort cab equipped GP40-2W for the Canadian National, and a small fleet of head end power equipped units for Toronto commuter agency GO Transit. Over the years, many GP40-2s have been de-turbocharged or have had their horsepower lowered to match GP38-2s, both to increase fuel economy and to make them less slippery at lower speeds.
By the mid 1970s, Amtrak was looking to replace their troublesome SDP40Fs. EMD had designed the F40PH, which basically a GP40-2 with a cowled car body and a built-in generator that generated electricity for passenger equipment. The F40PH proved very successful and reliable, becoming the standard Amtrak locomotive for over 20 years. Since they mechanically almost identical to the freight GP40-2s, maintenance and troubleshooting was also easy in the field. It also proved quite popular for regional commuter operations, with Chicago’s Metra fielding the largest fleet. Upgraded variants were introduced over the years which included the F40PH-2 and the distinctive slant-nosed F40PHM, the latter of which were the last locomotives built at EMD’s famous La Grange, IL facility in the late 1980s.
The GP39-2, like the GP39 before it, became the somewhat forgotten middle child. It’s 12-645E3 engine was rated, like all 39 series models, at 2,300 HP, and was a fuel-saving alternative to the 16-cylinder GP40-2 and GP39-2. Railroads took little interest, however, with only 239 built. It was certainly more popular than the GP39, but still represented a drop in the bucket compared to the thousands of GP38-2s and GP40-2s EMD was cranking out. The largest purchaser was the Santa Fe with 106. Later production GP39-2s represented some of the final 40 series Geeps built and had many external features in common with EMD’s next GP locomotive, the GP50.
Though not technically a Dash 2 model, another new 4 axle introduced during the 1970s was the GP15-1. During this time period, many railroads were rebuilding older GP7, GP9, GP18 and GP20 models rather than purchase new locomotives. EMD wanted in on this market and offered the GP15-1 initially as 1 for 1-unit replacement. Railroads could trade in older F and GP locomotives (along with a certain amount of money) and receive a GP15-1 in return. The GP15-1 was EMD’s version of a rebuild, but about the only things reused from the trade-ins were the trucks and frames. It featured a 12-645E normally aspirated engine rated at 1,500 HP and a very basic, pre-Dash 2 electrical system, denoted by the “Dash 1” designation. The locomotives visually resembled a smaller version of a GP38-2 but featured a lowered air intake system much like those used on the SD40T-2 and SD45T-2, giving them the nickname “Baby Tunnel Motors”. While not as successful as the railroad’s own rebuilding programs, the GP15-1 generated a respectable 310 orders, with Missouri Pacific (160) and Conrail (100) representing the lion’s share. Missouri Pacific also ordered 30 GP15ACs, a variant of the GP15-1 that utilized the same AR-10 AC alternator as the Dash 2 line rather than the older rebuilt DC D32 generator that was standard on the GP15-1. A turbocharged model was also built, the GP15T, which used an 8-645E3 engine rated at the same 1,500 HP as the 12-cylinder models. While marketed as a fuel-saving version of the GP15, the model only attracted sales to Chessie System (20) and Florida short line Apalachicola & Northern (3). These were also the only GP15 models built with dynamic brakes.
While bigger models were garnering most of the attention, EMD still fielded an end cab switcher for yard and local service. The SW series was supplanted by the MP series, the MP standing for “Multi-Purpose”. 3 variants of the MP were built between 1974 and 1987: the MP15 (later called the MP15DC), MP15AC and MP15T. All MP15s rode on the same frame as the GP15 and featured the Blomberg trucks normally found under a GP locomotive. The intent was the MP15 would be equally comfortable for crews in low speed yard service or higher speed road service, as well as having the option for a bathroom in a switcher. The MP15 was initially offered with a D32 DC generator, unlike the other Dash 2-line locomotives. Railroads wanted a model that used the same AR10 alternator as their Dash 2s, so the MP15AC was introduced, and the MP15 was re-designated MP15DC. Externally, an MP15DC has a single large air intake on its nose like an older SW model, while an MP15AC has “Tunnel Motor” style air intakes like those found on the GP15 line. Interestingly enough, MP15DCs and MP15ACs were built alongside each other for a few years, with some railroads not opting for the alternator equipped models. Both locomotives used the 12-645E engine rated at 1,500 HP. The last variant was the MP15T, which used the same 8-645E3 engine as the GP15T, also rated at 1,500 HP. All in all, 351 MP15DCs were built, along with 246 MP15ACs and 43 MP15Ts. The MP15 series would be EMD’s final offering of an end cab, purpose-built switching locomotive.
By the early 1980s, sales of the Dash 2 line were waning. Railroads were exercising caution when buying new locomotives, as fuel prices were rising and the entire future of diesel-powered locomotives was coming into question, though prices eventually came back down. Meanwhile, EMD began work on their successor to the 40 series, the 50 series. Unfortunately, the GP50 and SD50 were not reliable compared to the GP38-2s, GP40-2s and SD40-2s they were intended to supplant, and EMD lost serious market share as a result. GE introduced their new Dash 8 line of locomotives in 1985, and that year marked the first year GE outsold EMD. Though the 50 series problems were eventually ironed out, GE’s locomotives proved to be more popular, and EMD has been playing catch up ever since. The 40 series have stood the test of time, however, and the bulk of the GP38s, GP40s, SD40s and their successors are still in service today. Many have been rebuilt and modified extensively, while others continue to soldier on in more or less as-built condition. There are many SD45s still roaming the rails as well, but virtually all have been re-engined with 3,000 HP 16-645E3s. F40PHs continue to be the standard North Amercian commuter locomotive, while SW1000s, SW1500s, MP15s and GP15s have proven to be quite popular on the used locomotive market, as smaller railroads and industrial operations look to buy up reliable second hand locomotives. The 40 series were EMD at its very best, and the success of those models will continue to endure for years to come.
Thanks to Jonathon for both writing, as well as supplying all of the photos in the above article. This was a fantastic primer per say, on EMD’s golden years of locomotive production. We at VDD have not had much time as of late to do much writing as of late due to work travel (as always!), but please stay tuned. Lots of great articles in the works for this winter, as well as another “Series” I plan to start: Vintage Boat Documentation.