Gosh guys in reading your posts, I am not sure if you know what is in them. All it is is stuffed fiberglass. When the stuff wears out from
heat, it just shoots out the back and now it has no fiberglass stuffing to mute the sounds. They normally are gone within 6 months to a year in normal use.

There is no physical piece of glass that cracks or anything else that raddles.

Once the material is gone, the mufflers get real loud and mean.