With the advent of diesel traction in various areas of application in the USA, more and more diesel-powered shunting locomotives were procured. In the mid-range, the problem lay in a law requiring a second person in the cab to play the role of fireman for locomotives of all types of propulsion weighing 90,000 pounds and over. As a result, several manufacturers developed diesel shunters just below this limit, of which the 44-tonner from GE was the most well-known model.
In order to ensure an optimal view in both directions of travel, the driver's cab was placed exactly in the middle and raised. There was a hood on each side of the driver's cab, under which was a diesel engine with a generator. Most of the locomotives were powered by two Caterpillar D17000s with eight V-shaped cylinders and 180 hp each. With a maximum of ten pieces each, different six-cylinders were used. This was either the Hercules DFXD also with 180 hp, the Buda 6DH1742 with 200 hp or the Caterpillar D342 with 190 hp.
Of a total of 386 built vehicles, 276 went to US companies. 47 pieces were created from a special military variant that were delivered to the US armed forces. These had been given a lower cab for use in Europe and weighed down to 90,000 pounds. Of these, 31 were later sold to the Indian Railways and twelve to the Portuguese CP. The remaining four went to Australia, where they first came to the New South Wales State Railways and were listed as Class 79s. They changed hands several times and two of them ended up with the British Phosphate Commission where they were fitted with more modern Caterpillar D3306 engines in 1979.
