Catalytic converter possibly bad. How soon do I need to replace?

Question

2004 Cadillac SRX V8 AWD is making a rattling sound when idle, and mostly or completely goes away when RPMs increase. From what I've found, this is a bad catalytic converter.

It is under warranty still for this, when do I need to get it done?

Problem is that we have to take it 200 miles to get it replaced at the dealer. Is it bad to drive it at interstate or highway speeds to get there? How soon should this be done?

Answer 1

It sounds as if the internals of the cat may have broken loose. The catalytic converter is already broke so you can't make it any worse. The worst thing that can happen is it could the piece that is rattling may break free and plug the exhaust leaving you stranded. I would also ask the dealer if they will cover potential problems of a clogged muffler later on.