Mark Doiron

A bad catalytic converter (internally breaking) can also cause a rattling sound.

Twinkydog

You might also check the skid tab that goes under your crossover pipe. I keep bending mine up on my '11 until it just contacts the pipe.

DunnyBunny

Use a hose clamp. Exact same place mine was. Hose clamp will fix it.

zstairlessone

I have two clamps one on each end on my 3.8, cheaper and easier than tacking which would fail again anyway. Almost 20,000 miles with the repair and going strong.

CO Jeeper

x3 that it could be a heat shield.

My rattle came from the one near the muffler and seemed worse on colder days

The rattle is pretty much gone now after I bent some of it away from the exhaust (pretty easy to bend).

slednecks13

im having the same issue. i have a 07 jku just hit 80k miles. i brought it in when a check engine light came on and hes telling me its the catalytic converter. around 1500 rpm's when im trying to go a little faster it rattles then goes away when it kicks in and goes to 2500 3000 rpms. im going to bring it to a dealership to see what they say first.

tribulation138

Is the catalytic converter where the o2 sensors plug in?

Mark Doiron

Yes. On a 3.8 there are four catalytic converters. Two in each side of the exhaust before the Y-pipe. The entire assembly is what is replaced--collector from each exhaust manifold to the Y-pipe, including all four cats.