Hi everybody!

I've noticed that sound everytime when I start vehicle in the morning. It's not too loud like stunning sound but it's very annoing and people nearby can definately hear it. I've looked under the car and touched exhaust pipe in the middle of the car and it was vibrating and humming. However, the sound comes from the front part where the catalytic convertor is located. I've read somewhere that this sound is due to plates in cat.convertor warming up. After 4-5 min it goes away, I guess when cat warms up enough. I am afraid it will be longer wait and louder sound in winter. I wanted to order new cat.convertor, but no part stores can order it for some reason. Do I need to order it from dealer only? (I am afraid they will charge me a lot for that). Is there any aftermarket exact fit for that part?

It's 3.3 engine FLEXfuel, 4spd. auto, 2008 Dodge GC, SE model. (there is a thing that goes into cat.convertor - I guess it's an oxygen sensor?)

Thanks!