The DL-103 to DL-110 were the first diesel locomotives built by ALCO. The DL only stood for “Diesel Locomotive” and the individual models hardly differed from each other. The odd numbers stood for normal locomotives with cabs (so-called A-units), while the even numbers denoted the cab-less B-units or boosters. As with most American diesel locomotives of the time, the carbody was designed as a self-supporting construction with a streamlined front. The shape of the front with the three-piece windshield was designed by the German-American industrial designer Otto Kohler. All locomotives had an output of 2,000 hp, which came from two six-cylinder inline prime movers with turbochargers. Although four traction motors were sufficient to transmit the power, three-axle bogies, each with a carrying axle in the middle, were used, as in the EMD E series.

A total of 74 A units and four B units were built between 1939 and 1945. By far the largest proportion of these were the 60 A units ordered by the New York, New Haven & Hartford Railroad. All other customers received a maximum of four units, which were often used in front of prestigious passenger trains. The Second World War had made procurement difficult, since the production of purely passenger locomotives was prohibited and locomotives that were equally suitable for freight and passenger trains were also difficult to obtain. Finally, the New Haven only used their locomotives to haul passenger trains during the day, while hauling freight trains at night. Between 1949 and 1951 they were modernized and, among other things, the side windows in the engine room were removed, which were only used for decorative purposes. Despite this, the locomotives' service life was not very long, as they were soon replaced by more modern locomotives. Some were still visually matched to their EMD competitors, but most fell victim to the scrap press in the 1950s.

With the development of the new Type 244 engine, ALCO introduced the PA passenger locomotive in addition to the FA freight locomotive in 1946. Not only did the propulsion electrics come from General Electric, the streamlined and modern design of the car body also came from Ray Patten, head of GE's design department. The PA got the more powerful sixteen-cylinder engine and stood on two bogies with the A1A wheel arrangement. What all PA and FA have in common is that black smoke came out when accelerating due to the lack of air in the turbo lag.

With a 2,000 hp engine, 169 PA1 and 39 PB1 without a cab were built. From 1950 onwards, 81 PA2 and eight PB2 were built with 2,250 hp. Three PA-2s went to Brazil with a gauge of 5 ft 3 in. Some railroads also used their PA and PB in freight traffic, but the number of units remained behind EMD's E series due to lower reliability. The Massachusetts Bay Transit Authority used its locomotives until the late 1970s and then sold them to the Ferrocarriles Nacionales de México, which continued to use them until 1981.

The ten prototypes with the numbers D200 to D209 were delivered in 1958 as the first large diesel locomotives to be built in series by English Electric. They were based on the three experimental D16/2s completed in 1950 and 1954. The third example already had the 16SVT with 2,000 hp, which, like the bogies, was used for the production locomotives. The bogies, each with three powered axles, also had a carrying axle each in order to be able to carry the heavy weight. The locomotive body of the production locomotives deviated from the D16/2 and already had the shapes that were later to be found on the classes 37 and 55.

Another 190 production locomotives followed until 1962 as the D210 to D399, which later became known as the class 40. The first batch only received a vacuum brake system, the later ones could also pull cars with air brakes. Since they were intended for use in front of passenger trains, all received steam heating. Even during their testing, some people who considered the power for a large locomotive with such a high weight as too low. During the production of the last batch, the locomotives of classes 47 and 55 were introduced, which developed a significantly higher power at a lower weight without unpowered axles.

The Class 40 was primarily used in the north of England in front of high-value passenger trains. On the large main routes they were soon replaced by more powerful diesel locomotives, but on other routes they initially had no major competition due to their low axle loads. The lack of electric train heating became their problem from around 1980, as fewer and fewer passenger cars with steam heating were available. In contrast to the class 37, the class 40 was not modernized, so that larger numbers of decommissioning began and in 1985 the last examples disappeared from the scene. A total of eight locomotives were preserved, some of which are still operational today.

To speed up heavy passenger trains, China Railways started development of a heavy diesel-electric locomotive in 1990. After two DF9 prototypes built for a service speed of 140 km/h, the first DF11 built for 160 km/h was completed in 1992. At a weight of 138 tonnes, it is powered by a sixteen-cylinder with a rated power of 3,860 kW (5,176 hp), calibrated for 3,630 kW in the locomotive. Six DC traction motors have 3,040 kW (4,077 hp) in total.

On test runs, these locomotives could reach a speed of 184 km/h. A normal train load when running at top speed is 640 tonnes, but even passenger trains of 1,100 tonnes can be hauled at a speed of 143 km/h. As with previous Chinese locomotives, they can't deliver head-end power to the train, so separate generator cars are needed.

There is also a special plateau type for service on the highland plains in Western China. These have special filters for running through sandstorms, a slower gear ratio for a top speed of 153 km/h and engine modifications for greater power at altitude. Up to 2005, a total of 459 DF11 have been built for service in several regions of the country. Today they are still omnipresent on many non-electrified lines.

In 2009, the Argentine state railway Trenes Argentinos ordered 20 CKD8 diesel-electric locomotives from the Chinese company CNR, together with 220 passenger coaches for long-distance traffic. Although they have six axles, they are only intended for use in front of passenger trains.

The engine used is the MTU 16V 4000 delivered from Germany, which has an output of 2,200 kW. 13 CKD8G and seven CKD7G were built for different lines. The CKD8G reaches 120 km/h, while the CKD8H is designed for 160 km/h and therefore has a lower tractive effort.

Another order came from Nigeria in 2014 and included the CKD8 for the upgraded route between Abuja and Kaduna. These locomotives have been in service since 2018 and have a top speed of 150 km/h.

In 1935, EMC built a total of five machines to test the use of large mainline diesel locomotives under everyday conditions. These were two company demonstrators, one for the Baltimore & Ohio and a double set for the Santa Fé. Since there was no production capacity for large diesel locomotives at that time, they turned to General Electric and the St. Louis Car Company.

The basic idea was to install two diesel engines, each with its own generator and about 50 percent more total power, instead of just one diesel engine. Since the engines were less heavily loaded on average, less wear and tear and a longer service life could be expected. If one engine or generator failed, the locomotive could continue to run with the other. The concept of having a driver's cab at each end was new, but was not pursued on later American diesels.

For cost reasons, the two demonstrators had got simple, box-shaped bodies like earlier boxcabs. For the first time, they were given multiple controls, so that both locomotives could be controlled by one driver at the same time. In fact, they were often used together to achieve the same performance as a large steam engine. After extensive testing, they were scrapped in 1938.

The Baltimore & Ohio received a locomotive identical to the first two and was numbered 50. It soon got a slanted fairing on one end, also known as a “Shovel Nose”. This cladding was removed again during World War II. In this form, the locomotive was still used for local freight and passenger trains for a while after the end of the war. It later ended up in the National Museum of Transportation in St. Louis, Missouri and can still be found there today.

The double locomotive of the Santa Fé was managed as one complete unit and received the number 1. It had streamlined shapes, covered bogies and an attractive color scheme. The company's route network had long stretches that led through deserts and mountains and offered good conditions for testing the new technology. Their advantage over steam locomotives was that they were not dependent on water supplies and could cover long distances with one tank of diesel.

The 2,226.6-mile route, which was regularly run with passenger trains, served as preparation for the later operation of the streamlined trains and revealed a few teething problems. The fairing on the bogies soon had to be removed due to repeated overheating problems. The hood over the air intakes above the driver's cabs also impeded cooling, so that additional air intakes on the roof were necessary. The unit was later reinforced with one of the EMC demonstrators. In 1938, one driver's cab was removed and a “Bulldog Nose” formed, as was also found on the later production locomotives. In addition, both bogies each received a leading axle. The locos were returned to EMD in 1953 and converted to booster units.

The locomotives provided many insights which were implemented in the series production of the E series. These were powered by the same Winton engines, initially each with 900 hp, but bogies with a central carrying axle. The multiple control was soon adopted by all manufacturers and is still used today in almost all North American diesel locomotives in a form that has hardly changed.