In January 1972, EMD unveiled its “Dash-2” line, which heralded improvements in reliability and control systems. Previous model numbers were carried over, but with a “-2” suffix added to denote the improved model; the GP38 would become the GP38-2. In the original GP38, the diesel engine drove a generator to supply power to the traction motors, although an alternator was later offered as an option (the “GP38AC”). In the GP38-2, the 16-645E engine would drive an AR-10 alternator, with the AC electrical current from the alternator rectified to DC current to power four D77 traction motors on the trucks. Another major change was the “Dash-2” modular electrical cabinet, which sought to improve reliability and ease of maintenance. By the early 1970s, many of the locomotives from Baldwin, Fairbanks-Morse and Alco were considered obsolete and in need of replacement. Even the venerable EMD GP7s and GP9s were reaching the end of their service lives. The most common engine to replace them was the GP38-2.