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There is a maximum powered axle limitation to prevent pulling couplers apart
Hm, yes. Especially for so powerful machines as AC44's.
Otherwise, they should be put into middle of train or to the rear - as pushers.
And may I ask another questions. What is "manifest" trains? Going all their route length without set-outs/pick-up of extra cars?
Here, freight train's type is detailed in number-only code, but four digits seemed to be too few, IMO (as for number of train itself, only 99, or even less variants available). 1-high priority or container; 2-throug; 3-local; 4-light locomotives, maybe with empty cars:0; 5-transfer of cars to/from repair; 8-utility; 9-MOW trains.