I removed the dust cap off my MT today, and I know they are known for having tight gaps but I dont know if it is coil rub that causes it to make a, well can't describe the noise but only happens at high volumes, here are some pics.
No noise when I push it, but when I play it, it sounds like its //content.invisioncic.com/y282845/emoticons/crying.gif.ec0ebefe590df0251476573bc49e46d8.gif, I have a vid of it free aired here http://www.youtube.com/watch?v=YYlM-gWS1CM
Have you checked and made sure the spider is still firmly attached to the coil and basket? It could be a problem with one of the internal spiders. I have had spiders disconnect before and they sound almost exactly like that.