To date the GE AC6000CW is the most powerful single prime mover diesel locomotive that the company has attempted. The locomotive was built during the height of the horsepower race with EMD in the mid-1990s and as with its rival's SD90MAC model, GE's version proved to be troublesome and somewhat unreliable since the model was given little time to be properly tested and developed (GE had worked in conjunction with a foreign company to develop the new prime mover for the locomotive). Ultimately, General would build its last order to UP (the largest buyer of the model) with a de-rated prime mover that was more reliable. Interesting, today, with their problematic issues since resolved, most of the locomotives built for CSX and UP remain in operation (GE also found some foreign interest in the locomotive).
However, the locomotives no longer feature their as-built configurations. Both railroads have since overhauled the units; Union Pacific has now classified theirs as C44CM's while CSX has rebuilt their fleet with GEVO-16 prime movers for improved efficiency and environmental friendliness. They can now produce 5,800 horsepower and are classified as CW46AH's.
The GE AC6000CW was developed around the same time as both the C44-9W and the AC4400CW in the mid-1990s. The model was developed as a direct competitor to EMD's SD90MAC, as both models could produce 6,000 horsepower. During the early 1990s, to help develop the locomotive General Electric worked in conjunction with renowned engine manufacturer Deutz-Motoren Werke Mannheim (MWM) of Germany. By 1995 the first AC6000CW units were rolling out of the company's Erie, Pennsylvania plant with the first orders for both CSX and Union Pacific. The model's components and electronics were virtually identical to the AC4400CW and being that it was equipped with alternating current (AC) traction motors the AC6000CW could produce high tractive and pull heavy tonnage. The model was also one of the first to be equipped with the relatively new high-adhesion (or HT-C) truck, which helped to improve wheel-to-rail contact.
As with its sibling, the AC6000CW had a different designation than other models the builder produced, but the numbers and letter meant essentially the same thing. For instance, the "AC" referred to the model being alternating current, "6000" of course referred to its horsepower rating, the "C" referred to the unit having a C-C truck setup (three axles per truck), and the "W" designation meant it was equipped with the wide, safety cab. From an operational standpoint it provided the highest tractive effort of any main line locomotive up to that time, even more than the AC4400CW; 188,000 pounds starting and 166,000 using six of GE's model GEB13. Additionally, the design used the company high adhesion HT-C trucks.
Unfortunately, just as with EMD's SD90MAC the AC6000CW ran into serious reliability issues, mostly regarding the engine. With an engine block that was too small vibrations became a major issue, which resulted in other components failing or having problems. Because of this GE did not begin full production on the model until 1998 but by this point railroads were shying away from a 6,000-horsepower locomotive for a number of reasons; first, of course, was the reliability of either the AC6000CW or the SD90MAC; second was simply the actual efficiency of having just one locomotive pull an entire train (which both builders were trying to achieve). While the principal was sound on paper if that unit had mechanical issues of some kind and went down then the entire train would be stranded until relief could arrive.
By having, for instance, two 4,400 horsepower units (or more) hauling a train this issue was resolved. In the end, while most of the reliability issues were corrected, just a little over 300 GE AC6000CWs were built for CSX, UP, and SP (and another eight for an Australian mining company) by late 2000. And, it should be noted that UP's second order of AC6000CWs (which included 106 units) featured GE's more reliable 4,400 horsepower prime mover (listed by UP as AC4460CWs). Interestingly, despite their early mechanical issues most GE AC6000CWs soldier on for CSX and UP, albeit in rebuilt configurations. Lastly, for more information about the locomotive please refer to the chart above.