exhaust rattle...2.7L

I have a very loud exhaust rattle coming from under the cab after I put my automatic tranny in gear. Doesn't matter if it's "drive" or "reverse". Seems to happen mostly when the engine is cold but will still do it when warm as well just not as often. Also goes away when I accelerate.
Is there a "common" part that is causing this? Plan on getting underneath to check it out in the morning but just wanted to see if there was something I ought to be looking at first before I waste my time looking in the wrong areas!

 

Check the heat shield above your cats. My v6 has 2 catalytic converters. Not sure what the 2.7Ls have.

 

either the heat shield or the cat is actually bad, but I would think the CEL would be on it the cat was bad.

 

well i hope it's not the cat. I only have 68K on it. LOL I am throwing a code for the O2 bank 1 sensor, but it's been on for 3 years now!

 

i bought my 2010 in march, i noticed the same rattle the 1st time i started it after bringing it back home, goes away after it it warms up..... should i worry about that? maybe i should look at the heat shield when i get back home.

 

well, after thinking back to when I bought mine in jan 2004 I remmeber it doing the samething then and the dealer fixed it. Just not sure what they fixed or even how they fixed it. My only concern then was that the noise was gone.
I guess this is another one of those, "Tacoma" issues that most of us just live with like the rattle under the dash on the passenger side! and the coin tray always opening when you hit a rough patch of road.....LOL

 

ok went under the truck and found the issue. Seems that there is a bracket on the bell housing that extends to the pipe and there is a round clamp with a single bolt holding the 2 together. my clamp loosened up enough that it slipped off of the bracket and was resting on the O2 sensor.
Fix was easy. Just loosen the bolt a few turns place it back on the bracket and then stick a 12mm socket and extension between the top of the frame and the wheelwell where the small rubber splash shield is and tighten the hell out of it.

 

I used to have a rattle, it was my exhaust banging on my shackle/hangar