It is my understanding that the Southern Pacific liked the FT, but wanted automatic transition, and automatic shutters, which the FT's did not have. EMD advised that the next model would have those factors, which the F-3's did, and which the SP purchased. Sometime around 1943 the Southern Pacific made the decision to replace their steam with diesels. While they had refused to get on the FT "bandwagon", they changed their mind and purchase FT's for the Cotton Belt.