GE AC4400CW. The GE AC4400CW, , sometimes referred as "AC44CW", is a  diesel-electric locomotive that was built by GE Transportation Systems between 1993 and 2004. It is similar to the Dash 9-44CW, but uses AC traction motors instead of DC, with a separate inverter per motor.

2,834 units were built for North American railroads over an 11-year production. In 2005, all Class I freight railroads except Norfolk Southern and Canadian National owned at least one AC4400CW. Norfolk Southern ordered the very similar C40-9Ws, although NS would later acquire 36 former CEFX AC4400CWs in August 2023. As a result of more stringent emissions requirements that came into effect on January of that year, GE no longer offers the AC4400CW, replacing it with the ES44AC.

Design variations
The AC4400CW was the first GE locomotive to offer an optional self-steering truck design, intended to increase adhesion and reduce wear on the railhead. This option was specified by Canadian Pacific Railway, Cartier Railway, CSX for their units 201-599, Ferromex, Ferrosur, and Kansas City Southern Railway. The other railroads still used the hi-ad truck design

CSX ordered many of its AC4400CW locomotives with  extra weight to increase tractive effort. These same units were also modified in 2006-2007 with a "high tractive effort" software upgrade and redesignated CW44AH.

Rebuilds 
In 2017, Canadian Pacific Kansas City (then known as the Canadian Pacific Railway and simply Canadian Pacific) requested that General Electric modernize 30 of its 9500 and 9600-series AC4400CW units. The original units had the original front cab completely removed and upgraded to current GE standards with upgraded electrical systems including PTC and FTO systems. Other improvements GE has made include up to 10 percent fuel efficiency gains, 40 percent increase in reliability and 50 percent increase in haulage ability. The units were subsequently placed into service with the designation AC4400CWM (for Modernized). The first batch of rebuilds (8100-8129) also had their original Steerable trucks replaced with GEs High Adhesion trucks, where later batches each individual engine kept the trucks they already had. 

The following year Canadian Pacific Kansas City asked GE to similarly rebuild several more batches for a total of 110 locomotives. The second order (8130-8144) retains their steerable trucks. The third batch (8000-8064) will feature an Evolution Series sized fuel tank and radial trucks. In 2019 a fourth batch of rebuilds happened, 8145-8160 & 8064-8080 from the 95/9600-series. In 2021 both the 8500 series is slated to be rebuilt at 8201-8280 and the 8100-series be completed. 

The Union Pacific Railroad (UP) ordered many of their AC4400CWs with Controlled Tractive Effort software, giving them the designation of C44ACCTE. This software package is now standard on a portion of their ES44ACs as well. CTE limits tractive effort to mimic TE level of Dash series locomotives. In late 2023, they will all be rebuilt into C44ACMs.

In 2018, UP placed a small order for 20 rebuilds from GE of their AC4460CW fleet and later announced that they would be upgrading 1,000 of their AC4460CWs and AC44s into the new C44ACM class over the next 15 years. Unlike CP, the original 20 rebuilds did not receive a new crew cab.

CSX also placed orders to rebuild their large AC4400CW fleet. An initial batch of 10 AC4400CWs were rebuilt at Wabtec's Erie, Pennsylvania facility, with 40 more to follow. CSX continued the program and had received a total of 260 rebuilt locomotives by 2024. A final order has been placed to rebuild the remaining 200 plus locomotives and will be compled from 2024-2028. The rebuilds are numbered in the 7000, 7200, 7300, 7400, and 7500 series and CSX is referring to them as CM44ACs.

NS recently acquired 36 of these locomotives from CEFX in June 2023. They are currently being patched for starting service on the roster. These units will be rebuilt to AC44C6M locomotives (similar to the ones from the Dash 9 locomotives) at the Wabtec locomotive plant in Fort Worth, TX. The first unit, NS 3980, was the first unit to be rebuilt into an AC44C6M and it's undergoing testing at the Wabtec facility. NS planned to rebuild 25 of the 36 of these units, but they failed to be delivered to NS. They were sold to Wabtec then to FXE.

Operators
AC4400CW owners and operators past and present include:

In popular culture 
The plot of the movie Unstoppable required Denzel Washington and Chris Pine to climb aboard the lead locomotive of a runaway freight train. To film the movie, four Canadian Pacific AC4400CW locomotives (Nos. 9777, 9758, 9782, and 9751), were repainted as two fictional "Allegheny and West Virginia Railroad" locomotives (Nos. 777 (nicknamed "Triple 7") and 767). 9777 and 9782 were painted as 777, while 9758 and 9751 were painted as 767.

References 

Diesel–electric locomotives of the United States
General Electric locomotives
C-C locomotives
Railway locomotives introduced in 1993
Freight locomotives
Standard gauge locomotives of Canada
Standard gauge locomotives of the United States
Standard gauge locomotives of Mexico
Diesel–electric locomotives of Canada
Diesel–electric locomotives of Mexico