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?