The EMD F40C is a 6-axle diesel locomotive built by General Motors Electro-Motive Division between March and May 1974 for commuter rail service. It is powered by a 16-cylinderEMD 645E3B, which can produce 3,200 horsepower (2,390 kW). It uses the same frame as the EMD SD40-2, giving it an overall length of 68 feet 10 inches (20.98 m). All 15 examples were ordered by a publicly funded agency to provide for upgrading of service over Milwaukee Road lines west and north from Chicago to Elgin and Fox Lake Illinois. The units later became a part of the Metra locomotive fleet when that agency came to oversee heavy-rail commuter service in Northeast Illinois. All units of the type were withdrawn from regular service with the arrival of new MP36PH locomotives in 2003-2004. Thirteen locomotives were sold to locomotive leasing corporations, although units 611 and 614 were retained and kept on the property in the Western Avenuerailyard.
In the spring of 2009, units 611 and 614 were placed back into revenue service on both of Metra's ex-Milwaukee Road commuter lines. This is being done to cover schedules while the oldest units in Metra's EMD F40PH fleet are off the property being rebuilt. Along with a small fleet of HEP-equipped EMD SD70MAC locomotives operating on the Alaska Railroad, the F40Cs are the last six-axle passenger locomotives in daily service in North America.
The locomotives were ordered in two batches, EMD order numbers 73612 (13 locomotives) and 73689 (2 locomotives). They were all named in Metra service.