Yeah jerry, that's a big chunk of why i went to some RC hobby 6v motors as used in a rock crawler vs trying again with the 6v Industrial motors. Bearing, Windings, Brushes, Armatures, Magnets all aimed at making power, or just trying to squeeze more efficency and longevity into a gutless package.
Wow, i didn't know there were so many LeTournau toys that seem to use the same power-unit
http://www.tnttoytrucks.com/NYCONstruction.html
Should be fun to see what you'll come up with there
Travel speeds of similar vintage Euclids, bottom dumps start about middle of video.
https://youtu.be/YDfPw6DHTGw