A F9 can be distinguished reliably from a late F7 only by the addition of an extra filter grille ahead of the front porthole on the side panels on A units. Internally, the use of an 567C prime mover increased power to 1,750hp from the F7's 1,500hp.

By the time cab units such as the F9 were built, railroads were turning to the road switcher-style of locomotive, and the F9 was succeeded in most part by the EMD GP9.