FWIW, I do understand the desire as early on, I too wanted to use the railsounds boxcars to add sounds to trains that did not have them. I also have gotten some of the railsounds tenders for conventional engines.
I think possibly at least one of your railsounds boxcars is this https://www.lionelsupport.com/...am-RailSounds-Boxcar
6-19886
That little cylinder or hub on the axle is the magnet that triggers the chuff sound with rotation of the wheel
This tiny sensor at the tip of this circuit board is a Hall effect sensor that detects the specific magnetic poles of that rotating magnet ring on the axle.
