From what I can tell by peeking under the K-Lionel K4 is that the motor placement is the same but the thing has been re-geared to run very smoothly under Legacy control. This is another Lionel steamer that can be pushed by hand to roll the drivers. First engine I remember Lionel doing that with was the CCII ESE Hudson.
If Ted wants to start a K4 thread, I will pop the shell and snap some pics.