GE AC44C6M

The GE AC44C6M is an AC-traction 4,400-horsepower (3,300 kW) diesel locomotive, rebuilt from GE Transportation Dash 9 locomotives. AC44C6M rebuilds have been done by GE (now Wabtec), American Motive Power, Inc., and Norfolk Southern Railway's Juniata and Roanoke Shops, starting in September 2015. The AC44C6M retains the 16-cylinder 7FDL-16 prime mover used in the core locomotive prior to rebuilding, but replaces the Dash 9's DC traction motors with alternating current GE 5GEB13B7 traction motors. Externally, Norfolk Southern's Dash 9-40Cs received new wide-nosed cabs, and all rebuilt locomotives have a new hood front section with a new inverter cabinet behind the cab, while retaining the underframe and engine and radiator compartments of the original Dash 9 units.

GE AC44C6M
NS 4068 in Chesterton, Indiana[1]
Type and origin Power type Diesel-electric Builder GE Transportation Systems American Motive Power, Inc Norfolk Southern Model AC44C6M Build date August 2015-present Total produced Over 700 (hundreds more planned)
Specifications Configuration: ​  • AAR C-C Gauge 4 ft 8+1⁄2 in (1,435 mm) Trucks GE HiAd Wheel diameter 40 in (1,000 mm) Wheelbase 13 ft 7 in (4.14 m) Length 73 ft 2 in (22.30 m) Loco weight 432,000 lb (196 t), full supplies - (fuel oil, lube oil, sand). Fuel capacity 4,600 US gal (17 kL) Lubricant cap. 410 US gal (1.6 kL) Sandbox cap. 40 cu ft (1.1 m3) Prime mover GE 7FDL-16 Traction motors GE 5GEB13B7 AC
Performance figures Maximum speed 75 mph (121 km/h) Power output 4,400 hp (3,300 kW) Tractive effort 180,000 lbf (800 kN) (continuous) 200,000 lbf (890 kN) (starting)[2]
Career Locale United States Current owner Norfolk Southern, QNS&L, Fortescue Metals Group, Canadian National Railway, Union Pacific Railroad, BNSF Railway

Rebuilding an old Dash 9 locomotive into an AC44C6M costs only 50-60% that of purchasing a brand new AC locomotive.^[3] Wabtec claims a 17% improvement in fuel efficiency, 30% improvement in reliability, and a 55% improvement in haulage capability.^[4]

History

BNSF was the first railroad to order locomotive rebuilds with an order for 21 AC44C4Ms that were delivered in September 2015.^[5][6]

These were followed shortly by Norfolk Southern's AC44C6M's, which were first delivered at the end of 2015, and rebuilt from their Dash 9-40C locomotives.^[7] Norfolk Southern is the largest operator of the AC44C6M, with over 600 locomotives rebuilt as of 2022, and a further 330 by 2025.^[8] All of their Dash 9-40C units, and significant numbers of their Dash 9-40CW units have been rebuilt into AC44C6Ms. The railway plans to rebuild all of its remaining Dash 9–40CW units into AC44C6Ms. Norfolk Southern's AC44C6M locomotive features a new under-floor air conditioner, cab signals, LSL (Locomotive Speed Limiter), DPU systems, PTC, and ECP braking ability (on some units).^[9][10]

Quebec North Shore and Labrador Railway has 19 AC44C6M locomotives. These were rebuilt from former BNSF Dash 9 locomotives.^[11]

Fortescue Metals Group has 28 AC44C6M locomotives. These feature a larger radiator than other AC44C6M rebuilds.^[12]

Union Pacific also announced plans to rebuild 75 of their Dash 9 locomotives into AC locomotives, presumably AC44C6Ms, as part of a large order to rebuild much of their GE locomotive fleet.^[13] Union Pacific is a major customer of the similar AC4400CWM rebuild program. All of these locomotives are classified as C44ACM, which is similar to the C60AC (including convertibles) and C44AC rebuilds. All of the rebuilds use UP's new paint scheme that was introduced in late 2022.

A Canadian National AC44C6M rebuild was spotted outside of a Wabtec facility in early September 2022.^[14] This was later revealed to be an order for 50.^[15] 60 more units were ordered in 2023 for a total of 110. In 2025, 11 more units were ordered, raising the total to 121.^[16]

Similar rebuilds

The AC4400CWM is a similar rebuild program undertaken by GE/Wabtec, but starts with an AC4400CW or AC6000CW (UP only) instead of a Dash 9. Union Pacific, CSX, and CPKC have rebuilt several hundred AC4400CW into AC4400CWM models.

The AC44C4M is a rebuild similar to the AC44C6M, but AC44C4M locomotives feature 4 traction motors and an A1A-A1A configuration rather than the AC44C6M's 6-traction motors in a C-C configuration. This is similar to the ES44C4 and ET44C4 that BNSF also operates. These locomotives also retain their original cabs, with the exception of unit 616 as of 2025. BNSF has so far been the only customer of the AC44C4M, with 21 locomotives. They are numbered 599-615 and 617-619 and were formerly ATSF C44-9W units.

Operators

Railroad	Quantity	Road numbers	Notes
Norfolk Southern	996	3964–4366, 4368-4959 8520	Originally built as C40-9s, C40-9Ws, and AC4400CWs. They were uprated from 4,000 to 4,400 horsepower in 2013-2014. 4001 wrecked and subsequently repaired. 4063 wrecked in 2018 and retired. 4000–4005 & 8520 were painted into special paint liveries, 8520 classed as AC44C6CF and retains original cab; later retired and sold. 4822 was rebuilt in May 2024 and was repainted into the Honoring Railroaders paint scheme.[17] 4856-4880 were rebuilt from former GECX/BNSF Dash 9s in 2024. 3964-3999 were rebuilt from ex-CEFX AC4400CWs and were planned to deliver in 2025, but were never delivered to NS with 25 out of 36 units being sold to FXE. 4367 was renumbered to 4400 in 2020. 4851 was rebuilt in November 2024 and painted into the TAG heritage scheme. 4881-4959 have been ordered in 2025.
QNS&L	26	430-455	Originally built as BNSF/GECX C44-9Ws.
Fortescue Metals Group	28	101-128	Originally built as BNSF/GECX C44-9Ws. Feature larger radiators for expanded cooling capacity, similar to ES44ACi and ES44DCi.
Union Pacific	75	9500, 9600, 9700, 9800 series	Planned rebuilding of UP's C44-9W's. These are all classified as C44ACM.
Canadian National Railway	160	3300-3459	Rebuilding of CN/BNSF C44-9W. 3410-3459 were ordered in 2025.
Knoxville Locomotive Works (KLWX)	1	8520	Ex-NS AC44C6CF.
Ferromex (FXE)	60	4880-4939	Former NS. 25 units rebuilt from ex-CEFX AC4400CWs and 35 from D9-44CWs. These were rebuilt to NS specs but were never delivered to NS in 2025.
BNSF Railway	1	616	Rebuilt from a BNSF AC44C4M. Unit sold to Wabtec in Erie, PA as of 2018. Former ATSF.[18]

^[19]