I don't know what I did, but when I replace one of the ytd files, such as freight.ytd to use a modded train engine, the engine in game doesn't change from the default locomotive. Same with vehicle files. I changed it in the mod folder and even changed it in the core folder with no result. I do notice that when I look at the freight.yft file, the locomotive is the default, but none of the mods I'm downloading contain a yft file, just the ytd file. So none of the mods I'm trying will work at all. Any suggestions?