As the SD38, SD39, SD40, and SD45 shared a common frame, so too did the SD38-2, SD40-2, and SD45-2. It was longer than the previous models, giving a length of over the coupler pulling faces. The SD38-2 and SD40-2 shared the same basic superstructure, since they used the same 16-645 engine (in Roots-blown and turbocharged form respectively); the long hood was longer than the SD38 and SD40, but since the increase in frame length was even greater, the SD38-2 and SD40-2 had even larger front and rear "porches" than the earlier models. These empty areas at front and rear are spotting features to identify the Dash 2 models of both units. The SD40-2 can be distinguished from the SD38-2 by its three roof-mounted radiator fans instead of two, and a single large exhaust stack instead of two smaller stacks.