SD40-2 at a glance
| Builder | General Motors Electro-Motive Division (EMD); related production also came from GM's Canadian operation |
|---|---|
| Type | Diesel-electric road-switcher / freight locomotive |
| Power | 3,000 hp |
| Prime mover | EMD 16-645E3 family, turbocharged V16 two-stroke diesel |
| Wheel arrangement | C-C — two three-axle trucks, all six axles powered |
| Production era | 1972–1989 across the broader production run |
| Length | About 68 ft 10 in over couplers |
| Typical maximum speed | About 65 mph with common freight gearing |
| Typical fuel capacity | Roughly 3,200–4,000 U.S. gallons, depending on configuration |
Why the SD40-2 mattered
The SD40-2 arrived in 1972 as part of EMD's “Dash 2” generation. Its appeal was not simply raw horsepower. Railroads valued the combination of a proven 645-series engine, six powered axles and improved modular electrical controls that made troubleshooting and maintenance easier.
That balance of power, reliability and versatility allowed the model to work everything from heavy bulk trains to general merchandise and faster freight. Thousands were produced, and many units remained useful long after newer locomotive generations arrived.
How to identify an SD40-2
Six axles
Look for two three-axle trucks. In AAR terminology, that is a C-C wheel arrangement.
Long frame
The SD40-2 has noticeable “porches” at the ends of the long frame, especially compared with the earlier SD40.
Classic EMD shape
A conventional North American road-switcher body with a short hood, cab and long hood over the diesel engine and cooling system.
What does “SD40-2” mean?
SD identifies EMD's six-axle “Special Duty” road-locomotive family. 40 places it in EMD's 40-series family, and the -2 identifies the Dash 2 generation of improved electrical/control equipment.
Under the hood
The SD40-2 uses a turbocharged 16-cylinder EMD 645-series diesel prime mover. The diesel engine does not mechanically drive the wheels like a truck transmission. Instead, it drives electrical generating equipment, and electricity powers traction motors connected to the locomotive's axles.
This diesel-electric arrangement gives a locomotive the strong low-speed pulling ability needed to start and move heavy trains.
Horsepower vs. pulling power
The SD40-2 is rated at 3,000 horsepower, but horsepower is only part of the story. A freight locomotive must convert that power into usable tractive effort without exceeding the adhesion available between steel wheels and steel rail.
Its six powered axles help distribute weight and traction. Multiple SD40-2s could be connected and controlled together when a train needed more power.
Where did railroads use it?
Major North American railroads bought SD40-2s in large fleets, and the model became familiar across the United States and Canada. It could be found on coal trains, grain trains, manifest freight, intermodal service and many other assignments. Rebuilt and secondhand examples also found long careers on regional and short-line railroads.
SD40 vs. SD40-2
| Feature | SD40 | SD40-2 |
|---|---|---|
| Generation | Earlier 40-series design | Dash 2 generation |
| Horsepower | 3,000 hp | 3,000 hp |
| Axles | 6 | 6 |
| Major distinction | Earlier electrical/control system | Improved modular Dash 2 electronics and longer frame |
Quick facts
Power: 3,000 hp
Engine: turbocharged 16-cylinder EMD 645-series
Axles: 6 powered axles
Common top speed: about 65 mph
Era: introduced in 1972
Best known for: reliability, versatility and exceptionally widespread freight service.
Have an SD40-2 question?
Ask Ask the Conductor about horsepower, identification, train assignments, diesel-electric operation or how the SD40-2 compares with another locomotive.
Ask the Conductor