well at low rpm i get a really nasty rattle about were the cats at.
any ideas and ?

 

The catalyst inside your cat has become loose. How many miles does your jeep have? If it's below 150xxx I'd say you are probably running too rich and melted it down or overheated the engine and melted it. In other words if you're mileage is below 150xxx, the cat rattling is more than likely a symptom of another problem. Just replacing it will be a band-aid, and you'll have to replace the new cat soon too.

 

how old is the cat? when i first got my jeep the cat was toast.

 

well jeep has 151xxx mi or so and i drive it hard getting up to hi rpms dont think iv over heated the engine but maybe

and cat is stock oem

 

mine had 168,xxx plus and the inside of the cat was rattling aroud in it when i took it off to replace it and it was the stock one.

 

It may just be that the heat shield for the cat converter has rusted through and that's was causing the rattle. I just had a new exhaust installed, from the cat back, as it (cat converter) was still good. Began to get the rattle, especially when stopped at lights, intersections, etc. I took it in, and the heat shield had basically rusted loose, and was causing the rattle. Maybe that simple.

 

most exhaust shops will put it on the lift and diagnose for free around here atleast i would take it in and have it checked out hopefully its just a bad hanger

 

ok ty for help and tips if i get a min ill post a vid or some thing to

 

much more common than any of the above posts is that the exhaust pipe is rattling against the tranny crossmember because the bushing for the hanger that holds the pipe up has gone bad.

This one:

 

^These.