my muffler rattles from the inside when rev it up and at idal do you know what it is?

 

Maybe the baffles inside your muffler are falling apart or have come loose. How old is the vehicle and is it factory exhaust?

 

what kind of muffler is it? stock? because I have a dynomax turboflow and i think shes broken loose because at about 3200 its starts getting real tinny---just started doing that last week[:@]

 

Yopur sure its the muffler and not the cat?

Either way, it needs to be replaced.

 

I had a problem like that with my stock muffler. Just replaced it with an after-market catback exhaust system and the noise didn't happen anymore.

 

This happened to a truck that someone brought into the shop at my school. ended up just being a rock stuck in the heat shield. He had taken it to a muffler shop beforehand and they ha told him hed have to replace everything

 

yaa, very likely muffler or cat, my exhaust does the same thing [>:]
I need to replace my cat.....