| EMD SD45X | |
| Powertype: | Diesel-electric |
| Builder: | General Motors Electro-Motive Division (EMD) |
| Buildmodel: | SD45X |
| Builddate: | June 1970 to February 1971 |
| Totalproduction: | 7 |
| Aarwheels: | C-C |
| Uicclass: | Co'Co' |
| Primemover: | EMD 20-645E3A |
| Enginetype: | V20 diesel |
| Cylindercount: | 20 |
| Poweroutput: | 4200lk=inNaNlk=in |
| Locale: | United States |
An EMD SD45X is a 6-axle experimental diesel-electric locomotive built by General Motors Electro-Motive Division between June 1970 and February 1971. Power was provided by an EMD 645E3A 20-cylinder engine which generated 4200hp. 7 examples of this locomotive model were built for American railroads. 6 of these units would end up in service with Southern Pacific Railroad. One was rebuilt in 1980 by Morrison-Knudsen into an SD45Xm with a long hood from a scrapped DD35.
| 1 | EMD | 4201 | 6/70 | 36806 | EMD demo, to SP 9503, 12/72 |
| 2 | EMD | 4202, 4203 | 2/71 | 36807, 36808 | EMD demo, to SP 9504-9505, 12/72 |
| 1 | EMD | 5740 | 6/70 | 34123 | |
| 1 | Southern Pacific | 9500 | 8/70 | 35741 | |
| 2 | Southern Pacific | 9501, 9502 | 9/70 | 35742, 35743 | |