modifying talking Thomas trains

ok, so I have learned something new. and interesting.  
I started with
~4.5V (3 x AAA) going to the motor, then there are the resistors and capacitor.  I didn't bother looking them up cause... well what  do I know anyway?
here is what is interesting/strange:  I removed the resistor AND capacitor, put it all back together AND THE SPEED DIDN'T CHANGE... I swear.  I thought for sure that the removal of these would cause it to speed up.  I just wasn't sure what that would do to the voice part or if it would be too fast.  
So then I thought what the heck and swapped out the motor.  something about that caused issues with the voice part... so now I have the part.  I may try to add the capacitor and resistors back on and see what happens.  this is like a big jigsaw puzzle.  I suppose I could actually go learn more about circuits and understand better whats going on... but what fun is that?!?!?
if youre interested. this is what it looks like inside.
TTFN
  

BTW, is there any way to determine the RPM or speed of the motors that are in these guys from the factory?  I never know if the new motor is faster than the original.