In the 1980s, the EMD SD40-2 proved itself to be a very reliable product, but when the competitor, General Electric, developed more powerful and technologically advanced locomotives, EMD needed to keep up, and thus the SD50 was developed. However, the SD50 proved to be extremely unreliable, suffering from crankshaft and technological bugs and issues. EMD therefore commenced the development of the EMD SD60, along with a new prime mover, the EMD 710, to replace the aging EMD 645 design.
The original SD60 was almost indistinguishable from the SD50 from the outside; the differences are primarily in the prime mover (a 3800hp 16V710G3A two-stroke diesel engine) and new Dash-3 (Microprocessor) controls, in comparison to the SD50's 16V645F3B and Dash-2 controls.
The SD60 was considered a success; 1,140 were produced and many still continue in service today.
- Modified version with wide-cab. Early units used the Canadian "Tri-clops" widecab (named because of its 3 windows at the front), later units recieved the EMD Phase I safety cab (with 2 windows)
- An SD60M with the isolated cab to deaden the noise from the prime mover. They are identified by a rubber seal extending vertically on the nose.
- Canadian version of a standard SD60 with a cowl body to help with snow and ice. Features Draper taper carbody.
- AC version of the SD60M, often nicknamed by railfans as the "Mac". (Only 4 were built specially for the Burlington Northern, and inspired the development of the SD70MAC.)
- Rebuilt NS-designed wide nose and cab.
- SD60 series can often be confused for the SD50, one way to distinguish them from one another is by the the SD60's six latched access doors below the radiator. A smaller traction-motor blower duct separates the SD60 from SD70.
- NS 6920 is a recently rebuild SD60E which was also recently painted in a special commemorative scheme to honor US military veterans.
- NS 6963, another recent SD60E rebuild, wears the GoRail paint.
- As of mid-2011, BNSF has retired their fleets of former BN (Burlington Northern) SD60M units from primary service to serve as heavy-duty yard switchers as well as to be used for branchline service (besides also being saved and used as spare units).
The EMD SD60 series of diesel locomotives (excluding rebuilds) all have a 16 cylinder 710G series EMD engine; have a length of 71 ft 2 in (SD60), 71 ft 7 in (SD60M) and 74 ft (SD60MAC); have a fuel capacity of 4,500 US gallons.
All variants except the SD60MAC have 45 ft 10 in between truck bolsters; the SD60MAC has 50 ft 4 in.