I have searched and searched, but have not found much of an answer to this problem. Just noticed a few weeks ago that after I turn off the truck I hear a load ping/clang every 20 seconds or so. I crawled underneath the truck and put my ear close and pinpointed it to the drivers side catalytic converter, and it sounds just like somebody tapping it with a hammer every 20 secs or so. I didnt notice the manifolds or the cat glowing in the dark, but is this a sign that the cat is failing, or clogging? I did change the oil, plugs and seafoamed the truck a few weeks ago and hope the seafoam didnt cause this. Any ideas????

 

I have noticed something similar on my 03 Hemi with 124,000 and original catalytic converter. I live in St. Louis and temps have been in the 30-50 degree range and after a 40 minute highway commute, I pull in the driveway and it is popping right up where the catalytic converter sits. I can walk 50 feet up to my house and hear it for a few minutes until it cools enough. Next time I need to get under there and take a look to see if it is glowing or anything close.

 

It's the metal. Metal expands when hot and contracts when cool. After you shut your truck off, the metals are cooling down.

Lots of vehicles have that tick-tick-tick-clang type sounds when cooling down. My 2008 does it.

 

my 2007 ram does it some but the 1999 durango does it alot great question ive always wondered what that sound was

 

my 04 does this as well. my 2 buddies with the same year trucks dont do it at all. but i have had no issues so i just left it alone. glad i saw this thread and know that others have it as well. we all have around 100k on the trucks