The Arnold Jung Lokomotivfabrik also offered some diesel-hydraulic shunting locomotives in the 1950s, which were based on the Wehrmacht diesel locomotives. Two-axle vehicles with 300 hp, three-axle vehicles with 300, 400 and 440 hp and a four-axle vehicle with 600 hp were available. The designation of these locomotives consisted of an R for “shunting locomotive”, a number that indicated the approximate horsepower in tens and the letter B, C or D for the number of axles. There were also the RK 12 B and RK 20 B with chain drive. Although these were the first successful young diesel locomotives of the post-war period, the manufacturer referred to these locomotives as the “third generation” with regard to the former models from earlier times.

The R 42 C was the most successful variant of the series with 29 units. In reality, it had an output of 440 hp, which came from an eight-cylinder in-line MAN engine. This was the same engine like that used in the competing 440 hp Henschel and Krauss-Maffei locomotives. The Bundeswehr was the largest customer with seven vehicles. In contrast to their competitors, the young locomotives found fewer sales in industrial companies and were used more often on light and district railways.