Exhaust problem

rtbrick · June 2, 2003

One month after I purchased my 2000 Silverado I bought an aluminized Gibson split rear cat-back exhaust. Installed easy and sounded great. About 6-8 months later, the truck developed a thunk underneath somewhere. Same sound as if you firmly tapped the underside of the cab or bed with a rubber mallet. It started off just occasionally and became more and more frequent. I usually noticed it while stopped at a red light or simply stopped with the tranny in drive. I took it to the dealer and they finally traced it to a broken baffle in the muffler. I then called Gibson and ended up upgrading to the stainless version this past December. My other option was to purchase a new muffler for $85, send them my old one for analysis and if it was defective they would refund my $85.

Now here I am 6 months with the new stainless exhaust and I have started hearing the occasional thunk again. My luck IS such that I could get two defective mufflers, but I wonder if it could be something else. I called Gibson today and they said they do not have any complaints like this registered. They offered me the new muffler at $85 and the same analysis deal. Is there another component in the exhuast system that could be bad? Or even another part all together. I apologize for the lengthy post, but this problem is driving me nuts!

Bish · June 2, 2003

Could be a mounting issue with the exhaust. Best to get it on a lift and walk under it moving the exhaust around to see if it is close to the frame anywhere. I had a buzzing when I but my Borla catback on. A trip to my local Midas and they adjusted it for me while I watched. They didn't want any money but I flipped them a $20 for a case of beer. Never hurts if they remember you the next time. Mine has not made a sound since...of course any sound other than the nice throaty sound of Borla

Good Luck.

seadoons · June 2, 2003

From what you are describing it almost sounds like you are having the infamous driveline clunk problem. Does your truck have the nickel plated slip yoke installed on it? You might want to look into that. I'm like you, if I install something and I hear a new noise, I think it is coming from what I just installed. Sometimes though it is just coencidental that something else starts making a noise right when I install the new item...good luck!!!!

rtbrick · June 3, 2003

I have already had the yoke replaced. When I had this problem before it immediately went away when I first installed the stainless replacement exhaust.

bigtruck21 · June 3, 2003

let us know if it's another defective gibson. I was thinking about getting a system, but i'll hold out for a while now. Are you happy with the gibson gains by the way?

rtbrick · June 3, 2003

I believe the claimed gain is about 15hp. I really didn't notice a great deal of "seat of the pants" feel, but I had only had my truck one month before I swapped out the exhaust. A throaty exhaust note (but not overwhelming) and dual stainless tips out the rear were my goals. The sound is nice, not too loud, not much interior noise. Gibson stated that my problems are very much out of the ordinary. That's why I'm trying to see if the noise lies elsewhere underneath the truck.