I just got done replacing both y-pipe gaskets. However, I have a ticking sound from the driver's side cat. I had my wife gun it while I was under the truck. When I took a metal pipe and braced it against the cat and the frame, the sound goes away. Does this indicate a bad cat? This sound was there before I replaced the y-pipe gaskets, so I know it's nothing that I did today.

 

Yes. Bad cats. The insides are falling apart and rattle around inside.