The catalytic converters on my 2012 G37 sedan are rattling. It's been like this for 4+ years but getting worse and worse.
No codes were thrown so I've been just living with it since I heard it's an expensive fix. Rattle is only when idling or driving at low speeds.

I just went on eBay to search catalytic converters and lots are going for under $300! That seems like a reasonable price but I'm wondering why people say they cost $1000+
Are these aftermarket crappy ones or something? I live in Florida so I dont have any emission checks. I just want this rattle to stop.

Here are the ones I'm looking at. Some look different than others
https://www.ebay.com/itm/175884052608
https://www.ebay.com/itm/114573462501

Im guessing this one is the $1000+ stock one that people reference https://www.ebay.com/itm/296847337615 but i dont understand why anyone would buy this when they have others to choose from that are 1/3 the price.
Can some tell me the pros and cons of going with a cheap set?

 

Yes those eBay ones are crappy as they won't filter out the exhaust smell as good as oem and you'll probably get a check engine light in a few months for cat inefficiency. But if you don't care then they will be fine.

 

Catalytic Converters are actually more complex that many assume as they contain a mix of precious metals like platinum, palladium, and rhodium which act as a catalyst. I would stick with the more mainstream brands. If you are in CA, then they need to be CARB compliant, which means OEM ($$$$$$) or Magnaflow: https://www.magnaflow.com/products/5...nverter-551143

If you are in a state where Cats are required, yet some form of state compliance is not required, then there are High Flow Cat options. I think NY falls into this group.

Rock Auto has a decent selection: https://www.rockauto.com/en/catalog/...converter,5808

I would probably ask a local muffler shop and get their opinion as you will likely need them to assist with the replacement as these things get hot and tend to weld themselves in place over time.

I had to have one replaced under warranty years ago and the dealership spent the better part of the morning trying to get the old cat off the car.