The very first American Flyer U33Cs offered for two years had faster gearing than the follow-up versions that operated at better, slower speeds. All were Legacy models that were restricted to conventional AC, TMCC, or Legacy control. The more recent U33Cs and the U36Cs are listed as being DCC capable. I suspect that this means that they, like the SD70ACes and ES44ACs, can run also on DC in addition to DCC and the aforementioned control systems. I don't know this for sure, but I suspect that this is an additional difference from the first two years of production and the following two years also.
American Flyer got this extra compatibility before O gauge equipment did, and it should not be overlooked. The availability of scale wheels for diesels and some of the better detailed rolling stock is another indication that Lionel does listen.
