hey guys needs some opinions, have this rattle coming from undercarriage pretty sure its my cat but it only seems to do it when it drops into four cylinder mode. I do have and after market exhaust so it does vibrate and shake a little more when it bogs down to four cylinder. Jjust wanted to make sure its not the crappy transmission in this car making that noise. its hard to tell because I cant make it do it at idle because like I said only seems to do it in four cylinder mode so can only hear it on the fly and I have the noise be able to bounce back to me like off of a concrete divider or something. Let me know what anyone thinks thanks

 

Well I would think a transmission knocking or banging would be more prominent inside the car.. I know what you mean by only being able to hear it next to a divider or something..

Your best bet is to crawl under there and start smacking things around till you find the noise..

 

I would also be crawling under the car with a plastic hammer or something similar and start tapping the exhaust. Could be something a simple as a the heat shield . You can also (with help) Safely jack and support the vehicle and put it in gear an climb under the car , maybe that will help narrow down the noise. Good Luck