I just finished removing the crimped on heat shields from the passenger cats and the heatshield above the muffler and the f'ing thing is still rattling. I cannot figure it out...it must be the cats themselves. I think I need a H pipe...any ideas what else it could be? I've been under ther for hours and can't find it. Sounds like metal metal "fast" vibration...only when I'm slowing down 10MPH and under. Also right before I come to a full stop.

 

sounds like your Catlytic convertor started to deteriorate!

Time to replace them.

(Did you have a leaky Intercooler by any chance?)

 

I don't believe I had a leaky intercooler...why do you ask?

 

Do You Have A Stock Converter in the trans or aftermarket? it might be the conv. in the trans....JL

 

I have a stock converter...I had my trans services (drain, flush, refill) about 2 weeks prior to this noise starting. I don't hear any noise any other time, just when slowing down to about 10MPH to stop.

 

I had a nice rattle. Took it to the dealer, they gave me a new muffler. Rattle gone, under warranty.

 

I took it back to the tranny shop and the tech drove around with me. He concluded that it was a heat shield...thus I removed the ones we thought it was coming from. I have a Magnaflow muffler...I'm thinking it's the cats. I need a high flow pipe and some bassani!!! I'm really not looking fwd to spending the $$$ on it but this noise is driving me insane.

 

Hmmmm has not made the noise in a couple of days after I removed the shields. Did it once right after i removed them and has not done it since. Strange.

 

I'd try tapping or hitting everything with a rubber malet. I thought my cat was bad, but I tapped the mufler and it sounded like a coke can with a penny in it...

 

Ok...false alarm anyway...it just did it again on my lunch break.

 

im a rookie and everything, but my 2000 bolt did that for the first couple weeks i owned it. it would only rattle at a stop in drive. it was loud as hell and pissed me off. i never did find it and it went away. i have that underside coating on mine so its not as likley that it was underbody sheetmetal. i would HEAVLY suggest you check to see if your brake likes are hitting something. most likely a suspension component

 

Convertor.....I'd bet.

 

Weird. My 00 does this also but at around 70 MPH. It rattles loud when I press the accerator and then stop when I take my foot off. I thought it was my cats so I replaced them with Mag high flows thinking it would stop the problem. No such luck! My truck is in storage right now but once I get it over to Italy I'll have to start all over again looking to find this problem.

 

Good Luck. I'm going to have to replace my cats with high flows and get a new cat back. I have magnaflow single muffler now and I want something crazy loud to mask this noise if the exhuast doesn't fix it. already took off two cat heat shields and the heat shield above the muffler. I've spent probably 12 hrs under there looking for something loose.