s2kv

So I hear a rattle and took it to the dealer and they changed out the cat heat sheild, but that didnt solve the problem. What else do you think it can be guys? I hear it some times when just in neutral and in first gear at around 10mph it gets louder but when past 10-11 its gone and same in second gear at 20 mph. I also hear it when im slowing down in gear, like when in 3rd at 35mph and slowing down to a stop in 3rd I hear it too. It sounds like hmmm..... how can I describe it......like a rock in a tin can.

CKit

Did they check the cat itself? Sometimes the honeycomb breaks free and rattles. There's also a clutch rattle, but nothing you can do about that one.

s2kv

I dont think they checked the honeycomb in the cat. What else do you think it can be???

SpitfireS

I guess it IS the honeycomb core.
If you leave it that core may even damage your sec O2 sensor.

From what I read on this forum I understand your car is new enough to get a new cat under warranty.