So yesterday I was going through the McDonald's drive through, and when I roll down my window to pay the guy, I realize that my car's making a really loud rattle. It sounds like it's coming from under the cabin, in the vicinity of the tranny. When I get home, I messed around a little bit and figured out that it only does this when the car is in Drive, not Park or Neutral, so I thought it might be a tranny issue.

Then I talked to my friend, who said that when he had a pretty similar-sounding rattle on his Grand Cherokee, the guys at whatever shop he took it to replaced his cat, and the rattle disappeared. He apparently had stuff rattling around inside the cat. He also said that he only heard the rattle when his car was in Drive as well. So I thought that this might be the problem.

But, a few of my friends have told me that whenever I go WOT off the line (not that I ever do that ), I get a lot of brown smoke and a "bad smell" coming out of the exhaust, right before the tranny shifts into 2nd.

So, am I looking at two separate problems here, or could one or both of them be related to a problem with my cats? Or is it something different entirely?

Thanks!

 

My car has a similiar rattle at idle and I'm betting on it being one of the cats. Don't wanna spend the money to replace it when I'm gonna go o/r y-pipe in the future.

 

the smell sounds like cats.

 

Ok, thanks for the help. Anyone know if there is something specific I can test to see if it is the cats for sure?

 

you can test for backpressure, you have to tap into the exhaust pipe and hook up a gauge to it, before the cat. ha or you can take a hammer and hit your cat to see if it rattles.
-b

 

Just hit the cat and if it rattles.