In 1969 GE succeeded in bringing the 7FDL with 16 cylinders to an output of 3,600 hp. The first model was the U36B with only four axles, which was intended for fast freight trains. The Seaboard Coast Line bought 108 of the 125 U36Bs. With a total of 238 units, the U36C, which was suitable for heavier freight trains with six axles, was more successful. Most of the locomotives went to the ATSF and the Ferrocarriles Nacionales de México. The U34CH was a six-axle passenger locomotive with electric train heating. Since the engine had to run constantly at 900 instead of a maximum of 1,050 rpm when the power supply was switched on, the gross power was limited to 3,430 hp. 32 locomotives were built for the New Jersey Department of Transportation and another one was rebuilt from a U30C for the New York MTA.