In 2017,
Canadian Pacific (now
Canadian Pacific Kansas City) 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 AC4400CW
M (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 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 and 8064–8080 from the 95/9600-series. In 2021 the 8500 series is slated to be rebuilt as 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 were 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 completed from 2024-2028. The rebuilds are numbered in the 7000-7600 series and CSX is referring to them as
CM44ACs and
CM44AHs.
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 was undergoing testing at the Wabtec facility. 25 of the 36 units that were rebuilt were never delivered to NS, and were later sold to
Wabtec, then to
FXE. ==Operators==