The EMD SD70 series of locomotives began production in 1992, and is a six axle road switcher. Many variants of the locomotive were produced,and proved to be a reliable and safe design. The SD70 series was EMD’s answer to the C44-9W built by GE. This series also yielded the first AC traction locomotive built by EMD, the SD70MAC. The SD70MAC was pricier than the DC SD70 models because of the addition of the AC traction motors. The AC locomotives produced more pulling power and increased efficientcy. The SD70 series was also the first EMD locomotive equipped with HTCR trucks, which allowed the axles to steer themselves. This decreased wear on the wheels and the rails. Later, an updated version of these trucks were offered, called the HTSC truck, which was offered in the later SD70ACe and SD70M-2.
The standard SD70 locomotive uses a standard can design much like previous EMD locomotives, also called the “spartan cab”. However, the SD70 was equipped with computer screens and advanced electronics. This locomotive was equipped with DC traction motors, and has a EMD 710G3 prime mover producing 4,000 hp. 122 examples of this locomotive were built for Conrail, Illinois Central, and Norfolk Southern after the Conrail merger. In 2017, Norfolk Southern began an overhaul program converting SD70’s to SD70ACCs. This included the use of AC traction motors and updated electronics to accommodate the computer controlled, AC traction motors.
The SD70M locomotive was a widely popular unit among many railroads. This included the use of a wide cab design called the “North American Safety Cab”, replacing the standard, or “spartan cab” design. This cab is called the phase one cab and is similar to the cab used on the SD60M and SD60I. The phase two cab includes a more squared off nose portion, which allows for more head room in the nose of the locomotive. Railroads such as CSX, NYS&W, Norfolk Southern, Southern Pacific, and Union Pacific purchased the locomotives, with the largest order being from Union Pacific, ordering well over 1000 examples of the unit.
An isolated cab version of the SD70M was made called the SD70I, with Canadian National being the only railroad to purchase.
The SD70MAC was the first EMD locomotive to feature AC traction motors. This locomotive was EMDs response to GE’s AC4400CW locomotive. Many railroads were switching to AC motors because of their increased efficiency and reliability. The locomotives were more expensive than their DC counterparts because of the high cost of the inverters to supply the AC current. The locomotive was purchased by Conrail, BNSF, CSX, TFM, Kansas City Southern, and the Alaska Railroad. The Alaska Railroad ordered them with Head End Power to accommodate their use in passenger service.
The SD70ACe built upon the success of the SD70MAC, with AC traction motors. The SD70ACe had larger radiators much like the SD80MAC and SD90MAC series. The dynamic brake grid was also moved to the back of the locomotive. The SD70ACe was similar to the SD70MAC, except that it rode on a new under-frame. The piping and electrical cables were routed differently to make it easier to maintain. The SD70ACe was purchased by BNSF, CN, CSX, KCS, MRL, NS, UP, and Arkansas and Missouri Railroad. Some variations of these units include the SD70ACe-P4, which was designed to compete against the GE ES44C4. The SD70ACE-P4 included a A1A-A1A wheel arrangement, the middle axle of each truck was not powered, and lifted or lowered for better adhesion to the rail. The SD70AH was a heavier version of the locomotive, with the “H” denoting heavy. This locomotive was purchased by Union Pacific and weighed 8,000lbs heavier than a standard SD70ACe. The DC version of the SD70ACe is the SD70M-2, which was purchased by Norfolk Southern and Canadian National, 331 examples of this locomotive were built.
The SD70ACe-T4 meets the Environmental Protection Agency’s (EPA) tier 4 compliance standards. The locomotive features a 12 cylinder 1010J prime mover producing 4,000hp. The spotting feature of this locomotive is the top of the hood stands taller and is almost as tall as the radiator. Another spotting feature is that the locomotive utilizes a cab similar to the phase 2 SD70M. The Tier 4 locomotive competes with GE’s ET44AC locomotive. Railroads such as BNSF, Union Pacific, and CSX have began testing the units. The only railroad to receive their SD70ACe-T4 locomotives are Union Pacific, which placed an order for 100. Norfolk Southern and CSX have both placed an order for ten of the units.
Norfolk Southern has undergone a rebuild program converting SD9043MACs from Union Pacific into SD70ACUs. Rebuilds received updated electrical equipment and the phase 2 cab similar to the SD70ACe. For more information about the SD70ACU, check out NS Dash 9.
NS SD70ACU rebuild. Photo: CR 6377
Build date: 1992-
Wheel configuration: C-C
Prime mover:16-710. T4:12-1010J