Ted S, yes I did do exactly that on straight DC. And there was a pronounced difference in the low speed operation. The K-Line engines need far less voltage to the track to get moving as compared to the RMT versions.
I'm sure RMT did this as a reaction to all the complaints about the "jack-rabbit" running of the K-Line locos. And while you can get the K-Line locos to run slower by using a transformer with a lower starting voltage, the fact remains there are a lot of operators out there still using vintage Lionel transformers, that start off with 6-volts to the track.
Of course, here I'm excluding re-wiring the motors, or the later K-Line locos that came with a select power switch.
And YES, the RMT locos did have a select power switch on them. I suspect this was to accommodate operators who are using a command sort of set-up with the typical 18 volts to the track. Using a Lionel 1033 with the A-U voltage posts of 6-17 volts, and switching the power select switch on the RMT engine, you would NEVER ever have to worry about the engine flying off the track on a tight curve... it won't happen.
