For use in front of freight and express trains on the Gotthard, the SBB ordered the C 5/6, which was similar to the C 4/5 with a fifth coupled axle. Initially, three locomotives were built with four compound-acting cylinders and two with four simple-acting cylinders. The remaining 25 were built as compounds. Because of their power, they quickly earned the nickname “Elephant”. The 2901 and 2902 were also rebuilt into compound locomotives in 1920 and 1922, but did not achieve the same power as the others and were retired in 1933.

Since the Gotthard was electrified in the 1920s, the C 5/6 were relocated to the flatlands, where they were also used for heavy shunting duties. Since the Reichsbahn did not have enough locomotives for deliveries to Switzerland during the Second World War, 16 C 5/6s were leased to them. After the war, some were leased to France for the same reason. Their retirements took place between 1954 and 1968. Today there are two operational C 5/6 preserved and two more that are not operational.