I have this to at first I thought crap 2000 miles and my dif is going out luckily there's a guy at work that works on jeeps way more than any one else I know he knew seconds upon hearing it. said "heat shield, that empty metallic sound is a heat shield" so we got back and pulled up on the heat shield over the muffler and it went away. But! It has come back I have some days off next week and will remove the shield and see if I can " fix " it. If you've not messed with it the thing is slightly thicker that aluminum you cook with so any little bump or high speed wind will force it down. Now not saying I know this to be what is making the noise I just know when we forced it up from the muffler it stopped

 

Joshsolo might be right. I was thinking of something that happened to me (but not with a Jeep) and that was the catalytic converter. Ford truck I had had two of them. The guts come loose inside and rattle around under different pressures. Eventually the innards come loose enough to block the flow and the truck doesn't run well at all. Same kind of noise as the heat shield makes. Costs a fortune to replace.

 

I've had the same problem in my '07 for a while now. I've been under it multiple times looking for anything that might be sitting on the heat shield or something like that. I think I'm going to have to take it to the shop and have them check to see if its coming from the cat or the resonators. Will update when I know what it is

 

is your rear track bar hitting your passenger rear coil?

 

I have the same exact issue. It is much more noticeable when I am driving next to a building or another car. Haven't been able to figure it out either. It only happens when it is in gear and accelerating. If I let off the gas, it goes away. So that would tell me it has to be something with the transmission or diffs. It does it whether it is in 2wd or 4wd. So rear diff or transmission is my latest assumption on the source.

 

Had a similar issue a couple years ago on my tj. Turned out to be the drive shaft u-joints.

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Your exhaust crossover pipe has a heat shield with 6 or 8 spot welds. Look at these closely, if one is cracked it makes the noise some of you are describing. Either pipe clamp/reweld or just pry the shield away with a screwdriver. That little spot will make a helluva noise. Mine sounded like the tranny was fubared.

 

Thanks for the post.

I've got an '08 JKU with the same sound.

Thought I was hearing things.

I'll start looking underneath.

 

Did is you ever figure this out? I have the same noise

 

Metallic scraping sound when accelerating ... I have been searching my 2008 JK and the internet to get to the bottom of this problem. Found this old thread. Any solutions found?

Thanks in advance.