I also have a TrueHD audio track (movie soundtrack ripped from Blu-ray) and didn't get it to play in MC. Imported it through drag-n-drop from explorer into MC, but it imported as data. Changed Media Type to Audio, still when I tried playing it the Windows dialog asking which program I want to use to open the file appeared.
Tried changing the extension to .ac3, but MC still wouldn't play it (internal MC error message).
Your best bet is probably to use mkvmerge (part of mkvtoolnix) to put the file in a MKV container, unless somebody know of a file extension that lets MC play the file. Putting it into a MKV container shouldn't convert or change the audio format in any way.