The front/back bogies are seperate trains called EF-4 Sub-Truck or something and must be arranged under the little joe. It is VERY hard to put together.
Some assembly required, I'm not doing anything critical at the moment so I'm trying to dope out if it has a bug or not. Assembly in TS2010 requires placing the MILW-EF4-E75-70s, then connecting the MILW-EF4-Sub-Truck-Car-02 to the back of that, then coupling the MILW-EF4-Connecters-02 onto that to make a 3 car "train" of all the parts of the loco. Works fine in TS2010, for some reason it leaves a gap between the back coupler of the loco and whatever is coupled behind it in TS12. I'll probably post a bug report in the TS12 forum on this, but I doubt there will be any major loss of life or damage to property if I don't post it right away.