I'll also add- because it came up in another Lionchief RF only topic- this is one of those situations you might need the chokes on the motor wires so that EMI/RFI from the motor control doesn't block or interfere with radio range.
That's what's under the heatshrink on the motor leads- small inductors in series.
it is not a resistor even though Lionel parts listed it as such. It is an inductor. Appears to be 1.8uH in value based on the color bands.