On my 2003, from just after of the cat to forward of my muffler, this length of exhaust has a shield on it - about 3 feet.

If I tap it with a hammer, it rattles. And I can hear some kind of rattling at certain RPM and/or loads when I'm driving (not sure if the rattling is this piece of metal or not, maybe it's the cat shielding). At this point in time, I'm unsure if I've got pebbles trapped in there, or if some of the welds have come loose. Quite possibly it's both. I'm very likely going to just grab my grinder and ditch this shield altogether.

But that begs the question: does anyone happen to know why Ford felt compelled to wrap this section of pipe with shielding?? Seems rather odd to me.

 

#1 it helps slightly for cabin exhaust noise reduction and #2 it helps reduce cabin floor temperature when towing. Put a stainless steel hose clamp around it and no more rattle.

 

Just guessing, but to add to twigsV10 comments, it would also run cooler than the pipe itself (air space between), isolating heat from tall grass that can hit it when off the pavement.

 

I was going to add that but got lazy on the typing . I've had corn stocks smoldering on my old 94's exhaust with removes shields .

 

Police vehicles have had issues with parking on the side of the road and starting fires before as well because of tall grass. Small things like that prevent issues like that from popping up

 

I have the same rattling going on. Took me awhile to find it. I first thought it was an idler pulley or something in the engine bay, had me worried. It rattles all the time now, gives me a good excuse to tell the wife I need a new exhaust. Vroom Vroom!!

 

Perfect.
I didn't tell mine I had changed the exhaust and when she drove it a few weeks later without telling me she thought she had broken something because it made loud noises, lol

 

Ha. That's funny. How long did you play that card??

 

A few weeks, she doesn't usually drive my truck. By then I could say, "Oh, I did that a while ago."