After the AC-6 class cab forwards, 26 slightly larger AC-7 class machines were built in 1937. They were technically almost identical to their predecessors and differed visually in that they had a larger tender and a cab that was beveled at the front. The two frames of the locomotives were now cast together with the cylinders in one piece each. These were followed by 27 almost identical AC-8s, 40 AC-10s, 30 AC-11s and 20 AC-12s. The last AC-12 was also the last steam locomotive to be built for the Southern Pacific. These five subclasses were retired between 1954 and 1959. 