today i just noticed a rattle under my blazer. it doesn't rattle at idle, but when i touch the gas it rattles for a second then goes away. even in neutral it rattles so does that rule out the transfer case? i dont have a drop in gas milage like some people say they get with a bad cat. i looked under the truck and touched the gas with my hand (truck in neutral obviously) and the transfer case shook a little and i heard the rattle when i started it again it made the same noise. my other suspect is the cat. i still have my hesitation at low rpms too.
i tried searching other posts and couldn't really find anything exactly like this. if anyone has seen a post that goes over this or knows what this could be please let me know.

Edit: I realized this only happens when the engine gets warm, and my engine shudder only happens when the engine gets warm. i think thats more evidence that its my cat? i don't see a reason why it would be the trany because i have been nice to it lately :P