I had a problem like this. The 3.4 has a hanger that's supposed to keep it off of this metal brace. Best I can describe it. If they messed with the cat chances are it's gone. My exhaust pipe going from the manifolds back had to be lifted about halfway down the car. If you lay down on the passenger side and look up you should see it.

 

Sounds like your catalytic converters existing heat shield. Since you have no cat, remove the heat shield.

 

After reading this thread i looked under my car to see if it had cats.. I must say I'm very saddened to inform every one that it does

P.S: Some one went through all this money to put a nice aftermarket exhaust on this z just to put cats on with it (don't have smog test etc here).

 

Man, i got a lot of things to check this weekend! Im hoping its only one of them and I dont find 6 things about to fall off of my car lol but she's getting close to 200,000 so i guess its time for all these things to happen.

 

hope for the best, prepare for the worst. could be a lose flywheel cover, lol. lets see what else we can dream up,,,

 

I'm going to make it simple for you. Check your exhaust hangers.

I see a lot of high tech B.S. in everyone'e response to your problem, but most rattles comes from a loose exhaust system. Look there first.

 

ok so last night i had the car all jacked up, and went through my checlist of stuff that you guys gave me
1. the exhaust was slightly bumping on that cross member and the hanger where the catalytic converter was, was gone. i checked all the hangers (all good) and I fixed both of those (in a red neck fix) with some wire just to string it up to see if it fixed the problem. I drove it around and it didnt fix anything
2. checked the transmission mount, its just fine.
3. checked for CAT heat sheild, it was gone already.
4. im pretty sure its coming from my manifold... the problem is that i dont have the skill to take those off..... im hoping that one of the heat shields for those are just loose and i cant just tighten it or take it off.

Ill post a picture of my Redneck fix for ya'll =D

 

Get under the car with a rubber mallet and start whacking stuff. You'll find the rattler real quick that was. That's how I tracked down my heat shield rattle

 

Ok everyone i found it! the heat shield for the exhaust manifold was missing two bolts... pretty simple fix (:

 

This thread is high tech? Where?!!!!Lol

Op: glad you were able to track down the noise