Rich Batista's "All About the Trains" video does a nice job of showing the conversion steps necessary for a Lionel SD40. http://www.toytrainsontracks.com/
Here is a post of someone who did the install/upgrade on their set of SD40's. https://ogrforum.ogaugerr.com/...onel-s-legacy-sd40-s
Also, what model are you trying to convert?