Hubbry Logo
EMD SD90MACEMD SD90MACMain
Open search
EMD SD90MAC
Community hub
EMD SD90MAC
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
EMD SD90MAC
EMD SD90MAC
EMD SD90MAC
View on Wikipedia
from Wikipedia

EMD SD90MAC and SD9043MAC
Union Pacific 8540, an SD90MAC Phase II
Type and origin
Power typeDiesel-electric
BuilderElectro-Motive Diesel (EMD)
ModelSD90MAC
Build date1995–1999
Total produced657
Specifications
Configuration:
​
 • AARC-C
 • UICCo’Co’
Gauge4 ft 8+1⁄2 in (1,435 mm)
Wheel diameter45 in (1,100 mm)
Length80 ft 2 in (24.43 m)
Loco weight415,000 lb (188,000 kg) (SD9043MAC) and 425,000 lb (193,000 kg) (SD90MAC-H & SD90MAC-H2)
Fuel capacity5,000 US gal (19,000 L; 4,200 imp gal)
Sandbox cap.40 cu ft (1.1 m3)
Prime moverEMD 16-710 G3C-T1 and 16-265H
RPM range225-1,000 rpm
Engine typeV16 diesel
Traction motors6 Siemens 1TB2830 AC motors
Cylinders16
Cylinder size10.45 in × 11.80 in (265 mm × 300 mm)
Performance figures
Maximum speed70 mph (113 km/h)
Power output
  • SD9043MAC: 4,300 hp (3,210 kW)
  • SD90MAC: 6,000 hp (4,470 kW)
Tractive effortSmall engine (SD9043MAC): 185,000 lbf (820 kN) starting, 147,000 lbf (650 kN) continuous
Large engine (SD90MAC-H and SD90MAC-H2): 200,000 lbf (890 kN) starting, 165,000 lbf (730 kN) continuous

The EMD SD90MAC is a model of 6,000 hp (4,470 kW)[1] C-C diesel-electric locomotive produced by General Motors Electro-Motive Division (EMD). It is, with the SD80MAC, one of the largest single-engined locomotives produced by EMD and among the most powerful diesel-electric locomotives, surpassed only by the dual-engined DDA40X.

The SD9043MAC is the 4,300 hp (3,210 kW) variant, using a 16-cylinder 710G engine instead of the H-engine, which was originally intended as a temporary alternative while EMD tried to solve the H-engine's issues. However, the accompanying upgrade program was never utilized by its customers.

The SD90MACs features include radial steering trucks with AC traction motors and an isolated safety cab which is mounted on shock absorbers to lessen vibrations in the cab. The SD90MAC, like the SD80MAC, SD70ACe, and SD70M-2, has a wide radiator section, nearly the entire width of the locomotive, which along with their size makes them easy to spot.

As of 2019, some SD90MACs are still in service on the Union Pacific. Norfolk Southern had rostered 110 SD90MAC locomotives purchased or traded from Union Pacific or the CIT Group respectively, that have now all been rebuilt as EMD SD70ACU locomotives. Canadian Pacific has also opted to convert their small fleet of long-stored SD90MACs into SD70ACUs as well.

History

[edit]
Union Pacific SD9043MAC locomotive No. 8027

The SD90MAC was introduced in 1995, along with the SD80MAC locomotives. The SD90MAC was designed to utilize the new 16-cylinder H-engine, while the SD80MAC was designed to use the 20-cylinder version of the existing 710G engine. However, technical problems with the 6,000 horsepower (4,500 kW) engine resulted in the first locomotives being shipped with 4,300 hp (3,210 kW) 16-cylinder 710G engines, making them similar to the SD70MACs. These locomotives were informally designated SD9043MAC by railroads that purchased them with the option to re-engine them with 6,000 hp (4,470 kW) engines when they became available.[2] This upgrade program, however, was never taken advantage of by SD90MAC buyers due to reliability issues with the newer engine. Over 400 SD90MAC locomotives fitted with the 4,300 hp (3,210 kW) 710 engine were built.

In 1996, Electro-Motive Diesel entered full production on their 6,000 hp (4,470 kW), 16-cylinder H-engine, and all SD90MACs made from then on used that for its prime mover. Locomotives fitted with this engine are sometimes referred to as SD90MAC-H locomotives. Later versions of the SD90MAC-H feature a Phase II cab, with a new nose which offers higher visibility from the cab than the old nose. The SD90MAC-H did not prove popular with railroads and less than 70 were built, including Electro-Motive Diesel demonstrator units.

Since the SD90MAC-H had such a large prime mover, it didn't offer the same operational flexibility as smaller units, limiting its possible customer base to only the largest railroads. Also, since the H-engine was a new design, it hadn't reached the same level of reliability as EMD's previous engine. The low reliability on such a large engine was an especially bad combination since the loss of one engine in a train meant the loss of a larger percentage of pulling power than had a smaller engine failed. In the end, the SD90MAC-H was only delivered to two railroads; the Union Pacific and Canadian Pacific.[2] The Canadian Pacific locomotives were part of an earlier order for 710-engine equipped SD90MAC locomotives that was still in production when Electro-Motive Diesel switched over to the H-engine.

Electro-Motive Diesel also tried offering a lower-power version of the SD90MAC with a 12-cylinder engine called the SD89MAC, but none were produced other than the prototype.

Specifications

[edit]
Norfolk Southern 7332 in Ohio

Prime mover (EMD 710):

  • EMD V16 710G3C-T1
  • Power Output - 4,300 hp or 3,210 kW at 900 rpm
  • Idle - 200 rpm
  • Full Speed - 950 rpm

Prime mover (EMD 265):

  • EMD V16 EMD GM16V265
  • Power Output - 6,000 hp or 4,470 kW at 1,000 rpm
  • Idle - 200 rpm
  • Full speed - 1,000 rpm

Traction motors:

  • 6 Siemens 1TB2830 AC motors mounted 3 each on 2 HTCR-2 radial self-steering trucks.
  • Rated output - 855 hp or 638 kW
  • Gearing - 83:16
  • Wheel size - 45 in (1,143 mm)
  • Max revolutions - 3,435 rpm
  • Starting torque - 16,300 N⋅m or 12,022 lbf⋅ft
  • Continuous torque - 12,900 N⋅m or 9,515 lbf⋅ft
  • Maximum voltage - 2,183 V

Performance (parenthesis indicate H-Engine equipped specifications):

  • Maximum speed - 70 mph (113 km/h)
  • Starting tractive effort - 185,000 lbf (820 kN) and 200,000 lbf (890 kN))
  • Continuous tractive effort - 147,000 lbf (650 kN) and 165,000 lbf (730 kN))
  • Braking effort - 115,000 lbf (510 kN)[3]
  • Weight - 210 short tons (188 long tons; 191 t)/420,000 lb or 190,500 kg[4]

Fleet rosters

[edit]
Railroad Quantity Road Numbers Notes
SD9043MAC
Canadian Pacific 61 9100-9160 Units were at one time up for sale in "as is" condition, but no buyer was ever found. Some units had been intermittently placed into freight service to help combat motive power shortages.[1] 30 of them will be rebuilt in 2019 as EMD SD70ACUs and renumbered 7000-7029.[5] It was later announced that the order would be upped to 60 units in total, using the remainder of the 58 usable cores from the long-stored SD90MAC fleet and buying two SD90MACs from the Union Pacific to make up the difference. In 2021, Canadian Pacific purchased 40 more SD90MACs from Union Pacific for further continuation of the SD70ACU rebuild program.
CEFX 40 100-139 Units are on lease fleet. 10 units traded to Norfolk Southern for 15 MP15DCs.
Indiana Rail Road 14 9001-9013, 9025 These units are on long-term lease from CEFX. All to be retired and sold to NS for SD70ACU rebuilding.[6][7]
Norfolk Southern 110 7229-7338 NS purchased 100 units in September 2014 from EMD/Progress Rail. Those units are ex-UP. 10 units were acquired from CEFX in June 2016, in exchange for 15 MP15DCs. All units have been converted to SD70ACUs. 65 of them sold to PRLX. 30 of the PRLX units were sold to Ferromex in 2024. Unit 7314 was renumbered to 7339.
Union Pacific 309 8000-8308 Most of them were renumbered 3470–3775 to make room for new GE ES44ACs. Both the Norfolk Southern and Canadian Pacific have purchased locomotives from Union Pacific's fleet for SD70ACU rebuilds; in September 2014, Norfolk Southern purchased 100 of these and in 2019 and 2021 Canadian Pacific purchased 42 of these in total.
Fortescue 5 905-909 Ex Union Pacific 8527, 8530, 8531, 8541 & 8554, rebuilt from SD90MAC-Hs at Juniata Shops[8]
SD90MAC-H
Canadian Pacific 4 9300-9303 These were scrapped in Lachine, QC. [2]
EMLX 40 8500, 8523-8561 Former Union Pacific 8500, 8523-8561, currently stored. All leased to Kansas City Southern (KCS) in 2008 on a one-year lease. Several went to the Buffalo & Pittsburgh Railroad upon returning from KCS lease. All currently stored. 8522, 8527, 8529-8531, 8539, 8541, 8549 & 8554 sold in 2011 to Fortescue in Western Australia.[8][9][10] Have since been sold to many different owners, primarily for scrap.
Union Pacific 62 8500-8561 Fleet Retired, some after less than 5 years of service. 8500, 8523–8561 to EMLX Lease fleet, 8501-8522 renumbered 8911-8931. Retired in late 2008-2009. Sold to Metro East Industries in Alorton, Illinois. Scrapped mid to late 2009.
Fortescue 4 901-904 ex Union Pacific 8522, 8529, 8539 & 8549, rebuilt Juniata Shops[9][11]
SD90MAC-PII
Fortescue 8 910-917 Ex Union Pacific 8538, 8548, 8550, 8557, 8525, 8533, 8543 & 8547, rebuilt by Progress Rail, Mayfield, Kentucky, all scrapped 2022[12]

Current status

[edit]
Norfolk Southern SD70ACU No. 7305. The SD70ACU was part of Norfolk Southern's SD90MAC rebuild program.

As of January 2005, the SD90MAC is no longer in production due to the Environmental Protection Agency's Tier 2 locomotive emission regulations, although EMD had planned to be able to get the H-engine approved at some later date. However, China recently announced an order for 300 JT56ACe locomotives, which also use the H-Engine as its prime mover. A portion of the locomotives will be assembled in kit form by China's own Dalian Locomotive Works. These units were reportedly capable of meeting the EPA's strict regulations and began delivery in the latter half of 2007.

Due to reliability issues, Fortescue units 910 to 917 were stored. They were purchased to be used as slave units, and were more offline than they were in use. All were scrapped in 2022.[12] As at October 2024, six SD90MAC-Hs remained in service with two in store.[13]

On 1 August 2008, Union Pacific announced that it would be retiring 21 of the SD90MAC locomotives. Common parts will be used to maintain the railroad's 710-engined SD90MAC fleet. The 265H prime mover will be cut up or exported. The only part that is not reusable is the frame. These units, in the 8900 series will be removed from storage in Denver, and will be sent to East St. Louis, in small batches to be dismantled. As of 2019, Union Pacific still operates some of the remaining SD9043MACs, which sport new numbers and UP wings on the cab. These units take the original road numbers of the Union Pacific's original SD40-2 fleet.

Canadian Pacific's SD90MAC-H locomotives 9300-9303 (listed as SD90MAC6000s) were up for tendered sale in 2009. The bidding ended 31 March 2010. While they were originally thought to be shipped overseas, they were eventually moved to Quebec for scrapping.

Canadian Pacific's SD90MAC locomotives, numbered in the 9100–9160 series had been in long-term storage in Winnipeg, Manitoba, for much of the 2010 decade. Three units, the 9129, 9133 and 9138, were scrapped in November 2012 due to errors in preparing them for long-term storage. The entire fleet had been put up for sale in November 2012 and again in January 2013 with no offers being received. These units remained stored until the winter of 2018 when at first 30, then all 58 remaining units entered a rebuild program to be converted into SD70ACUs. In 2021, Canadian Pacific purchased 40 more SD90MACs from the Union Pacific for further rebuilding into SD70ACU engines.

In September 2014, Norfolk Southern purchased 100 4300 hp SD9043MACs from Union Pacific with the intent to rebuild them into SD70ACUs at the Juniata Shops. The last four SD90MACs were delivered to Norfolk Southern on October 3, 2015, running parallel to Western Avenue in Chicago.

In 2015, Cummins rebuilt a single SD90MAC with its QSK95 engine, designed to meet Tier 4 emissions standards. Sygnet Rail Technologies and Brookville Equipment Corporation performed the conversion. The rebuild was designated HTL4200AC. The locomotive, numbered CECX No. 1919, had been Union Pacific No. 8559.[14]

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

EMD SD90MAC

View on Grokipedia
from Grokipedia
The EMD SD90MAC is a six-axle (C-C) AC-traction diesel-electric freight locomotive manufactured by General Motors Electro-Motive Division (EMD), producing 6,000 horsepower (4,470 kW) for heavy-haul service. Introduced in 1995 as EMD's most powerful single-frame locomotive, it utilized the innovative 16-cylinder 265H four-stroke diesel engine to deliver high tractive effort, with starting pull up to 205,000 pounds and continuous at 137,000 pounds. The model measured 80 feet 2 inches in length, rode on HTCR-II high-traction trucks with 40-inch wheels, and had a top speed of 70 mph, making it suitable for demanding freight operations on major North American railroads. Development of the SD90MAC followed the successful SD70 series and marked EMD's push into higher-power AC technology, with production spanning 1995 to 2000 and totaling around 410 units across variants, including the related lower-powered SD90-43MAC; however, due to reliability issues with the 265H engine, only a limited number were built at full 6,000 hp, with most utilizing a 4,300 hp 12-cylinder 710 engine. Primary operators included the , which acquired 309 SD90-43MAC units, and Canadian Pacific, which purchased 61 such locomotives, alongside 40 leased through . The locomotive's design emphasized reliability and efficiency in , intermodal, and bulk freight , though later rebuilds addressed early engine challenges to extend service life; as of 2025, rebuilt units continue to operate on select railroads.

Design and Development

Background and Introduction

The EMD SD90MAC is a high-horsepower, six-axle AC-traction diesel-electric developed by General Motors' Electro-Motive Division (EMD) during the mid-1990s, amid an intense "diesel power race" between EMD and rival . As EMD's response to growing demands from Class I railroads for locomotives capable of handling heavier freight loads with fewer units, the SD90MAC targeted heavy-haul applications such as , , and intermodal trains, where high and reliability were paramount. It succeeded the popular SD70 series by introducing advanced microprocessor-controlled systems and AC drive technology, enabling superior and sustained performance on challenging routes. The model's nomenclature—"SD90MAC"—encapsulates its design intent: "SD" denotes a six-axle configuration optimized for special-duty freight service, "90" refers to its 6,000 horsepower rating, though many early units were derated to 4,300 hp using a different engine due to development delays with the intended prime mover, and "MAC" refers to microprocessor-based controls combined with AC traction motors. This evolution positioned the SD90MAC directly against GE's AC4400CW, which had gained traction through its 4,400 hp output and robust AC systems, prompting EMD to emphasize higher power density and electronic integration to capture market share among major North American carriers seeking to optimize train consists for efficiency and cost savings. Production of the SD90MAC ran from to , yielding approximately 500 units, primarily the SD90-43MAC variant, with fewer than 70 equipped with the 6,000 hp 265H engine, for North American railroads alongside additional export variants tailored for overseas heavy-haul operations. This output reflected the era's push for in design, with the SD90MAC's steerable trucks and high-adhesion features briefly referenced as key enablers for its role in demanding freight corridors, though detailed are covered elsewhere.

Engine Evolution

The development of for the EMD SD90MAC represented a pivotal shift in engine technology, moving from the proven two-stroke series to the more powerful four-stroke 265H series to meet demands for higher horsepower in heavy-haul service. Announced in 1994, the 265H engine was designed as a 16-cylinder unit with a 265 mm bore, twin turbochargers, and a target continuous output of 6,000 hp, enabling greater than prior EMD designs. Due to unresolved reliability issues with the 265H during prototype testing, early production units adopted a derated 16-cylinder 710G3B rated at 4,300 hp, allowing the SD90/43MAC to enter service while further development continued on the new . This interim solution ensured timely delivery to operators like Union Pacific, which received the first units in 1997, though plans for retrofitting the 265H were ultimately abandoned owing to persistent challenges. However, the 265H struggled with EPA emissions compliance, limiting its use and leading EMD to prioritize refined 710 variants for broader adoption. After rigorous testing, the 265H core was integrated into the SD90MAC-H configuration in late , successfully achieving its 6,000 hp continuous rating and marking EMD's entry into high-output four-stroke for locomotives. Key technical hurdles, including overheating under sustained loads and elevated emissions levels, were tackled through iterative redesigns, with significant improvements realized by 1997 that enhanced and compliance for limited production. The 265H offered higher power but faced challenges with emissions and fuel consumption, leading to limited adoption.

Structural Innovations

The EMD SD90MAC featured HTCR-II radial trucks designed specifically for heavy-haul service, incorporating a self- mechanism that aligned the end s with the direction of travel on curved track to minimize wheel flange and rail wear. This system utilized traction rods connected to a steering beam, allowing the outer axles to pivot up to 0.5 degrees for improved radial alignment, which reduced lateral forces and compared to conventional rigid-frame trucks. Yaw dampers further stabilized the assembly at higher speeds, enhancing curve negotiation without the need for active hydraulic actuation, though the bolsterless design with rubber compression springs distributed the locomotive's weight evenly across all six axles for optimal traction. The locomotive's cab design emphasized crew safety and visibility, employing an isolated North American Safety Cab (NASC) mounted on shock absorbers to dampen vibrations and shocks during operation. Early Phase I units, produced from 1995 to 1996, incorporated a sloped wide-nose profile that improved forward sightlines while meeting Association of American Railroads (AAR) crashworthiness standards through reinforced structural elements. Subsequent Phase II cabs, introduced in 1997, refined this with a revised two-piece windshield for even better visibility, a taller entry door, and enhanced AAR-compliant features such as anti-climber couplers and energy-absorbing side structures to protect occupants in collisions. This evolution addressed operator feedback on ergonomics, positioning the crew higher relative to the rail for reduced glare and expanded field of view. Supporting the SD90MAC's substantial power output, the frame was a reinforced high-tensile integral (HTSI) structure capable of handling a loaded weight of approximately 210 tons (420,000 pounds), ensuring durability under high-adhesion heavy-haul conditions. The design shared foundational elements with the SD70 and SD80MAC series but included extended length (80 feet 2 inches overall) and beefed-up underframe components to accommodate the larger prime mover and fuel capacity. Cooling provisions were scaled accordingly, with a large area optimized for dissipating the elevated heat from the H-series engine, featuring high-capacity fans and ducting to maintain during prolonged operations. Safety features advanced through the integration of the EM2000 microprocessor control system, which represented one of the first widespread implementations of such technology in EMD's AC-traction locomotives for precise management of wheel slip and dynamic braking. This system monitored individual axle speeds via Doppler radar and sensors, automatically adjusting traction effort to prevent slippage on low-adhesion rails, thereby maximizing starting tractive effort (up to 200,000 pounds) without derailment risk. For dynamic braking, the EM2000 coordinated regenerative and resistive modes across the AC motors, blending effort to extend brake shoe life and control descent on grades, with failover protections ensuring reliability in multi-unit consists.

Technical Specifications

Prime Mover and Traction Systems

The prime mover of the EMD SD90MAC is the 16-265H, a V-type 16-cylinder four-stroke developed by (EMD), rated at 6,000 horsepower (4,470 kW) at 1,000 rpm with an idle speed of 200 rpm. This engine features a bore of 10.45 inches and a of 11.80 inches, designed to deliver high for heavy-haul freight service while integrating with advanced AC traction technology. The prime mover drives the TA22 main alternator, which converts mechanical energy to electrical power with an output capacity of approximately 6,400 kW to support the locomotive's propulsion demands. The traction system employs six EMD 1TB2830 (Siemens design) three-phase AC traction motors, one per axle, each rated at approximately 1,000 kW and mounted on HTCR-II radial self-steering trucks for improved adhesion and stability under load. These inverter-controlled motors enable variable-speed operation through from dedicated traction inverters, allowing precise control across a wide speed range and contributing to the locomotive's high starting . The AC design enhances efficiency and reduces maintenance compared to traditional DC systems by eliminating brushes and commutators. The EM2000 microprocessor-based manages throttle response, wheel slip protection, and overall locomotive performance, processing inputs from the , , and traction to optimize power delivery. Integrated provides regenerative capability, generating up to 115,000 lbf (510 kN) of braking effort by converting back to electrical power dissipated through roof-mounted grids, which supports extended braking without excessive reliance on air brakes. Auxiliary systems include the 74F16 generator, which supplies 74-volt DC excitation for the alternator, and a head-end power (HEP) system delivering 480 volts AC for cab comfort features such as lighting, ventilation, and control electronics. These components ensure reliable operation of non-propulsion functions, maintaining crew environment and system integrity during long-haul operations. Note: Specifications in this section pertain to the 6000 hp SD90MAC-H variant; the more common SD90-43MAC uses a 4300 hp 16-710G3B with adjusted metrics (see ).

Dimensions and Performance Metrics

The EMD SD90MAC is a large six-axle diesel-electric designed for heavy-haul freight service, with physical dimensions optimized for stability and compatibility with standard North American rail . Its overall length over the couplers measures 80 ft 2 in (24.43 m), providing ample space for the extended hood and cab configuration typical of EMD's SD-series. The width is 10 ft 3 in (3.12 m), ensuring clearance on most mainline routes, while the height to the top of the cab reaches 15 ft 7.5 in (4.76 m), accommodating the tall cooling system required for its high-power prime mover. The locomotive's operating weight is 420,000 lb (190,509 kg), distributed across six axles for an axle loading of 70,000 lb (31,751 kg) per axle, which maximizes on tracks rated for Class I railroads while minimizing wear. This weight distribution contributes to the SD90MAC's ability to handle heavy in configurations. Performance metrics highlight the SD90MAC's capabilities as a high-traction unit, leveraging AC traction motors for superior pulling power. It delivers a starting of 200,000 lbf (890 kN) at 33% , enabling rapid of long freight trains. Continuous stands at 165,000 lbf (734 kN). The governor limits top speed to 70 mph (113 km/h), balancing operational demands with safety on mixed-traffic lines.
MetricValue
Fuel Capacity5,000 US gal (18,927 L)
Sand Capacity (total)40 cu ft (1.13 m³)
These capacities support extended operations: the allows for long-haul runs without frequent refueling, while the sand reservoirs provide traction enhancement for slippery conditions, with delivery to each rail via the HTCR-II truck design.

Variants

SD9043MAC

The SD9043MAC is a derated variant of the EMD SD90MAC , featuring a power output of 4,300 horsepower derived from a 16-cylinder EMD 710G3B prime mover. This configuration was introduced in 1995 as an interim solution to address delays in the development of the more powerful 16-265H intended for the full 6,000 horsepower SD90MAC model. The 710G3B , a reliable two-stroke diesel also used in models like the SD70 series, allowed production to proceed without compromising immediate availability for customers seeking high-traction AC . Production of the SD9043MAC spanned from October 1995 to February 2000, with a total of 410 units constructed, primarily for , which received 309 examples numbered 8000–8308. Canadian Pacific acquired 61 units numbered 9100–9160, built by in , while 40 went to CIT Leasing numbered 100–139. These locomotives shared the same wide-nose cab and HTCR-II high-traction trucks as the standard SD90MAC, but incorporated a detuned and electrical systems calibrated for the lower , enhancing overall reliability compared to early prototypes plagued by H-engine issues. Operationally, the SD9043MAC filled a niche in mixed freight services where the full 6,000 horsepower of the H-engine variant was deemed unnecessary, offering robust for heavy-haul duties while sidestepping the reliability concerns associated with the unproven four-stroke . Its emphasized and compatibility with existing EMD fleets, making it a practical choice for railroads prioritizing consistent operation over maximum power.

SD90MAC-H Configurations

The SD90MAC-H configurations represent the full-rated 6,000 horsepower variants of the SD90MAC family, powered by EMD's 16-cylinder 265H prime mover, a high-bore designed for superior and emissions compliance. These configurations were produced in two phases, distinguished primarily by cab design evolutions and refinements to address early reliability concerns. A total of 68 units were built, including two demonstrator prototypes that entered . Phase I units, constructed from August 1996 to 1999, totaled 22 locomotives delivered exclusively to Union Pacific, numbered 8500-8521. These featured the initial wide-body cab with a sloped front profile for aerodynamic efficiency and basic crew protection, mounted on shock absorbers to isolate vibrations. However, the early 265H engines in these units experienced significant cooling issues, including overheating during sustained high-load operations due to inadequate heat dissipation in the radiator system. Phase II production, spanning 1998 to 1999, encompassed 46 units: 40 for Union Pacific (8522-8561), four for Canadian Pacific (9300-9303), and the two demonstrators (EMDX 8204 and 8205, later renumbered to UP 8914 and 8920). Refinements to the H-core engine included improved piston seals and cooling enhancements to mitigate prior overheating problems, enabling more reliable performance at full rating. The cab was updated with a revised nose section for enhanced , including better sightlines and control layouts, alongside improved through reinforced structural elements compliant with emerging federal standards. These configurations incorporated unique features such as an enlarged dynamic brake grid, positioned in a prominent hatch on the roof, to support sustained high-effort braking in heavy-haul applications without thermal overload. Software updates to the engine control systems further optimized and management for reduced emissions, aligning with EPA Tier 0 standards. Beyond initial deployments, several Union Pacific Phase I and II units have been rebuilt and exported to , where they influence modern heavy-haul locomotive designs for transport, often with upgraded cooling and AC traction components.

Production and Deployment

Manufacturing Overview

The EMD SD90MAC series was primarily assembled at the company's facility, which served as the main production site for locomotives following the shift of assembly operations from , in the late , while La Grange continued to handle design, engineering, and component manufacturing. During peak years, the London plant achieved production rates of 10 to 15 units per month in 1996 and 1997 to meet surging demand from major railroads. Production began with prototypes in 1995, following a development timeline that started in and culminated in the first units entering testing shortly thereafter. Full-scale peaked between 1996 and 1998, with the majority of the approximately 410 units completed during this period as railroads sought high-horsepower AC-traction locomotives to replace aging fleets. Output gradually declined after 1998, extending until 2005, when stricter EPA Tier 2 emissions standards prompted a transition to compliant designs like the SD70ACe. Key components for the SD90MAC were sourced from specialized suppliers, including traction motors produced at their U.S. facilities, integrated into EMD's system. The 16-265H prime movers, intended for the 6,000 hp variants, were assembled at the London plant in , leveraging local engineering expertise for the design. In the , the cost per SD90MAC unit was estimated at approximately $2.5 million to $3 million in contemporary dollars, influenced by factors such as custom configurations for specific operators and the inclusion of advanced AC-traction components. These figures reflected the for high-power models during the era's intense competition between EMD and .

Primary Operators and Rosters

The EMD SD90MAC, including its de-rated SD9043MAC and H-engine variants, saw its largest deployment with Union Pacific, which acquired a total of 309 SD9043MAC units between 1995 and 2000, numbered UP 8000–8308, alongside 22 SD90MAC-H units numbered UP 8900–8921. The first production unit, UP 8000 (serial number 936449-1), was built in October 1995, marking the start of deliveries from EMD's La Grange, Illinois facility. These locomotives formed the backbone of UP's heavy-haul operations, with build dates spanning from late 1995 to January 1999 for the SD9043MAC series and 1997 to 1998 for the H variants (serials primarily from 966002 and related orders). Canadian Pacific ordered 61 SD9043MAC units, numbered CP 9100–9160, delivered between October 1998 and February 1999 to support freight services across its network. The initial batch of 12 units (CP 9100–9111, serials 976842-1 to 976842-12) was constructed by (GMD) in , while the remaining 49 (CP 9112–9160, serials 976842-13 to 976842-61) were assembled by CP at its Ogden Shops in , , using kits supplied by EMD. Norfolk Southern acquired 110 SD90MAC locomotives in the mid-2010s through purchases from (ex-Union Pacific trade-ins) and CIT Leasing, initially numbered NS 7229–7338, to bolster AC-traction capacity amid high traffic volumes. The core fleet of 100 units arrived in (ex-UP 8000-series, serials primarily from 936449 and 956613 orders), with an additional 10 from CEFX in 2016 (serials from 986927 order). These were deployed in general freight service before subsequent rebuilds. Smaller rosters included leasing arrangements with other Class I railroads. BNSF operated 10 SD9043MAC units on lease from CIT Financial (CEFX 100–109 subset), primarily in 2000–2005 for and intermodal trains, though not as owned assets. CSX briefly rostered 5 units (leased from Helm Leasing, ex-EMD demonstrators or early production), used in tests and short-term service around 1996–1998. Exports extended the model's reach, notably to , where 300 JT56ACe locomotives—based on the SD90MAC-H design with the 16-265H prime mover—were produced from 2005 to 2008 under a between EMD and Dalian Locomotive and Co. These were numbered in the HXN3 series for , with the first deliveries in 2007 for heavy-haul applications.
OperatorVariantQuantityRoad NumbersBuild DatesKey Serial RangeNotes
Union PacificSD9043MAC3098000–83081995–1999936449-1 through 976800-130Largest fleet; many renumbered to 3470–3778 in 2008.
Union PacificSD90MAC-H228900–89211997–1998966002-1 to 966002-10 and relatedH-engine prototypes; some traded to EMD.
Canadian PacificSD9043MAC619100–91601998–1999976842-1 to 976842-6112 by GMD, 49 assembled by CP.
Norfolk SouthernSD9043MAC1107229–7338Acquired 2014–2016 (built 1995–1999)Various ex-UP/CEFX100 ex-UP via , 10 ex-CEFX.
BNSF (leased)SD9043MAC10N/A (CEFX marks)1999986927 subsetShort-term lease for service.
CSX (leased)SD90MAC5N/A1995–1996Early productionTest and temporary use.
JT56ACe (H-based)300HXN3 series2005–2008Joint EMD/DalianExported for heavy freight.

Operational History

Early Service and Challenges

The EMD SD90MAC entered in late 1995 with the , which received the initial deliveries of SD90-43MAC variants starting in October of that year. These locomotives were primarily assigned to trains operating in Wyoming's , a key region for heavy-haul unit train operations. The design's three-phase AC traction motors and HTCR-II radial steering trucks delivered superior adhesion levels—dispatchable at 33%—enabling fewer units to haul massive 15,000-ton consists compared to previous DC-powered models like the SD40-2. This capability addressed the Basin's challenging grades and curves, reducing wheel slip and improving overall efficiency in low-speed starts and heavy pulling scenarios. Despite these operational advantages, the SD90MAC faced significant reliability challenges from its debut, particularly with the 16-265H prime mover intended for the full 6,000 hp SD90MAC-H configuration. Introduced in limited numbers starting August 1996, the H-engine suffered from persistent overheating, crankshaft failures, and cooling system inadequacies, leading to frequent breakdowns and extended downtime during the first years of service. Union Pacific, which acquired 40 such units, experienced substantial disruptions, prompting warranty claims against (EMD) and contributing to the engine's rapid abandonment by the manufacturer. As a result, many early orders were fulfilled with the more dependable 16-710G3B engine at 4,300 hp, reclassifying the locomotives as SD90-43MACs to ensure fleet viability. Canadian Pacific Railway introduced SD90MACs into service around 1998, deploying them on diverse freight assignments including intermodal and bulk commodities over the challenging mountain grades of the Canadian Rockies. While the locomotives' high starting —rated at 200,000 pounds—proved beneficial for ascending steep inclines, operators encountered mixed performance due to inconsistent power delivery and electronic control sensitivities in varying altitudes and temperatures. Adaptations, such as refinements to the EM2000 microprocessor-based , were applied by late 1998 to mitigate these issues, including temporary fleet inspections and software optimizations for better response and thermal management. CP ultimately scaled back its order to just four units, reflecting caution amid the ongoing teething problems observed across operators. These initial hurdles underscored the risks of pushing horsepower boundaries, but paved the way for iterative improvements in AC locomotive technology.

Rebuilds and Modernizations

initiated a major rebuild program in 2015 to address reliability issues stemming from the original 16-265H prime movers in its SD90MAC fleet, converting 110 units to SD70ACU configuration by 2019. These rebuilds, performed primarily at NS's Juniata Locomotive Shop with four units handled by EMD's Muncie facility, replaced the problematic H-series engines with proven 4,300 horsepower 16-710G3B diesel engines, along with upgraded electrical systems including inverters and alternators for improved performance and reduced maintenance. The program enhanced the locomotives' operational dependability, transforming them into a core component of NS's heavy-haul operations. Canadian Pacific Railway launched its own modernization effort in 2018 through a partnership with , rebuilding 60 SD90MAC units into SD70ACU variants between 2019 and 2021 to extend their service life and incorporate emissions compliance features. The initial order covered 30 locomotives using stored SD90MAC cores, with the program later expanded by acquiring additional units from Union Pacific; these rebuilds involved remanufacturing the existing engines, updating traction systems, and adding aftertreatment kits for reduced and particulate emissions. Delivered starting in mid-2019, the upgraded units featured raised walkways for better snow clearance and were renumbered in the 7000-series, bolstering CP's freight roster with more efficient, environmentally adapted power. Union Pacific, having retired most of its SD90MAC fleet due to early service challenges, redirected surplus units in the by returning them to EMD's lease fleet under the EMLX , where approximately 40 locomotives were stored or leased to short-line operators pending further disposition. Additionally, 17 units were exported to for Fortescue Metals Group, where they underwent rebuilds in the early to 4,300 horsepower configurations using 16-710 engines, adapting the SD90MAC-H variants for heavy haulage in the region with modifications for harsh environmental conditions. In the 2020s, continued overhauls on remaining SD90MAC components, focusing on engine and system upgrades to support ongoing rail and industrial applications. By 2022, at least 33 SD90MAC locomotives had been scrapped, primarily due to frame fatigue and obsolescence, with scrapping concentrated at facilities like those operated by CD Dodd in .

Current Status

Active Usage in 2025

As of November 2025, the maintains approximately 35 active SD90MAC-H locomotives in its fleet, primarily utilized in helper service on grades in the , with the remainder of its original SD9043MAC units having been rebuilt or placed in storage following post-2024 fleet audits. In , Fortescue Metals Group operates a small number of rebuilt SD90MAC derivatives, with only two units (901 and 902, reconfigured as SD9043MACs) remaining active for heavy on lines, despite significant scrappings of 15 others between 2022 and September 2025. Fortescue Metals Group retired and scrapped 7 exported units post-2023, including FMG 904 in May 2024, with parts from these locomotives repurposed in SD70 series rebuilds to extend the life of those models. Lease fleets and shortline operators have largely phased out their SD90MAC units; for instance, Leasing (EMLX) retains a handful of SD90MAC-H locomotives on its roster for occasional assignment, while the continues to run 13 leased SD9043MAC units as of mid-2025, with several retired by July and the remainder facing potential scrapping or restoration amid locomotive issues as of November 2025, as newer motive power replaces them. Niche heavy-haul applications persist in with remnants of rebuilt SD90MAC fleets on select Class I lines, but no new production has occurred since the early ; overseas, China's JT56ACe (HXN3 class) derivative remains robust, with a significant number of the original 332 units actively serving on and freight lines. As of , approximately 20-35 original SD90MAC locomotives remained in , with additional derivatives in service overseas; most have been retired or rebuilt into lower-horsepower variants.

Retirement and Legacy

The retirement of EMD SD90MAC locomotives occurred in several waves, beginning with the Union Pacific Railroad's decision to retire its 21 SD90MAC-H units in 2008 amid reliability issues and economic pressures from , leading to their scrapping by 2009. Extensive rebuild programs further diminished the original fleet; Norfolk Southern converted over 100 SD90MAC units to SD70ACU configuration at Juniata Locomotive Shop by 2021, while Canadian Pacific rebuilt approximately 58 units to the same standard between 2018 and 2021, reducing unmodified examples to near zero. By 2022, a total of 33 SD90MAC locomotives had been confirmed scrapped across , with many processed at Progress Rail facilities in , where components were salvaged for reuse. As of 2025, no SD90MAC units are preserved in museums. Athearn announced detailed model kits of the SD90MAC in 2025, reflecting continued enthusiast interest in the type. The SD90MAC's legacy lies in its role as a high-horsepower pioneer of AC traction technology, which it helped popularize despite operational challenges, directly influencing the design of the more reliable, lower-powered EMD SD70ACe introduced in 2005. Production of the SD90MAC ceased with the implementation of EPA Tier 2 emissions standards in 2005, which the model could not meet without significant redesign, shifting focus to compliant successors like the SD70ACe.

References

  1. https://www.american-rails.com/956626.html
  2. https://www.progressrail.com/en/Company/AboutUs/EMD100/1990s.html
  3. https://www.railwayage.com/mechanical/progress-rail-to-upgrade-cp-units/
  4. https://www.american-rails.com/sd90mac.html
  5. https://www.thedieselshop.us/Data%20EMD%20SD90MAC.HTML
  6. https://www.railwaygazette.com/news/emds-first-6000hp-locos-enter-revenue-service/27534.article
  7. https://www.athearn.com/on/demandware.static/-/Sites-athearn-us-Library/default/dw3b81d536/announcements/may-2025/01_GENHO_SD90MAC_052325.pdf
  8. https://www.railwaygazette.com/in-depth/us-loco-market-still-a-two-horse-race/29327.article
  9. https://trains-and-locomotives.fandom.com/wiki/EMD_SD90MAC
  10. http://www.okthepk.ca/dataCprSiding/articles/200307/trucks.htm
  11. https://www.scribd.com/doc/97083029/Service-Manual-EMD
  12. https://fr.scribd.com/document/329108067/Diesel-Electric-Loco-SD90MAC-EN-pdf
  13. https://www.mobility.siemens.com/us/en/portfolio/rolling-stock-components/traction-motors.html
  14. https://www.progressrail.com/en/Segments/Locomotive/LocomotiveElectronics.html
  15. http://www.sd80mac.com/sd90mac/stats.html
  16. https://okthepk.ca/dataCprSiding/articles/200307/specs.htm
  17. https://utahrails.net/up-diesel-roster/up-diesel-roster-66.php
  18. https://www.trainweb.us/galt-stn/cproster/locomotive/9100s/9100.htm
  19. https://railfan.com/last-dance-for-indiana-sd90macs/
  20. http://www.sd80mac.com/sd90mac/roster.html
  21. http://www.utahrails.net/up-diesel-roster/up-diesel-roster-67.php
  22. http://www.rrpicturearchives.net/locolist.aspx?id=CP&mid=60
  23. https://utahrails.net/loconotes/close-lagrange.php
  24. https://www.american-rails.com/emd.html
  25. https://utahrails.net/up-diesel-roster/up-diesel-roster-67.php
  26. http://www.okthepk.ca/dataCprSiding/articles/200307/history.htm
  27. https://forum.trains.com/t/why-did-up-choose-the-70-macs/48964
  28. http://www.nsdash9.com/atroster.html
  29. http://www.nsdash9.com/rosters/7229.html
  30. https://railroadfan.com/wiki/index.php/SD90_Series
  31. https://enmobile.prnasia.com/releases/global/Electro_Motive_Diesel_Inc_EMD_Introduces_the_New_JT56ACe_High_Power_Diesel_Electric_Locomotive-13147.shtml
  32. https://www.trains.com/wp-content/uploads/2023/09/Locomotive-2009.pdf
  33. http://www.altoonaworks.info/rebuilds/ns_sd70acu.html
  34. https://www.pwrs.ca/announcements/view.php?ID=17435
  35. https://www.trains.com/pro/mechanical/locomotives/10-altoona-sd70acu/
  36. https://www.progressrail.com/en/Company/News/PressReleases/progressrailsignscontractwithcanadianpacificfor30modernizedlocom.html
  37. https://www.trains.com/pro/mechanical/locomotives/22-first-canadian-pacific-sd70acu-locomotives-delivered/
  38. https://modelrailroadnews.com/canadian-national-and-norfolk-southern-sd70acu/
  39. https://www.pilbararailways.com.au/FMG/fmg.php
  40. https://www.trainorders.com/discussion/read.php?1,1856222
  41. https://www.progressrail.com/en/Segments/Locomotive/LocomotiveServices/Locomotive_Remanufacturing.html
  42. https://www.pilbararailways.com.au/FMG/roster.php
  43. http://www.rrpicturearchives.net/locolist.aspx?id=UP&mid=60
  44. http://www.rrpicturearchives.net/locolist.aspx?id=EMLX
  45. https://www.thedieselshop.us/INRD.HTML
  46. https://www.facebook.com/groups/indrrbs/posts/3737229303239782/
  47. https://trainspo.com/model/hxn3/
  48. https://forum.trains.com/t/sd-90-macs-being-scrapped/181913
  49. https://www.athearn.com/product/ho-gen-sd90mac-h-ph-i-locomotive-legendary-liveries-mkt-800/ATHG-2558.html
  50. https://www.trains.com/trn/railroads/locomotives/the-evolution-of-emds-sd70-series-locomotives/
  51. https://www.american-rails.com/20106364.html
Add your contribution
Related Hubs
User Avatar
No comments yet.