rattle undercarriage
 

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