D500 posted:Williams diesels are among the easiest locos to upgrade to TMCC and Railsounds by way of ERR kits (sold by 3rd Rail, as mentioned). Comes with instructions (probably on-line, actually, at this point - so check those out before you order).
Good first-timer project. You can even use the Williams speaker, in place.
I'm interested in upgrading a Williams by Williams 212 Santa Fe Alco unit that the horn stopped working, I ordered and replaced the sound board from Bachmann and now all it does is screech. I checked the ERR kits and the RailSounds Commander sounds like what I need but I'm not sure it'll work because they all state they are Lionel compatible but nothing about Williams. Anyone smarter than me know what I need?