Cat Replacement?

Mike534x

Original poster
Member
Apr 9, 2012
894
Hey everyone! Since work hours are crap right now, I'm looking at tackling the next job on my to-do list.

So, when I bought my Envoy back in 2017 its had a bit of metallic "buzzing" sound coming from the passenger side of the truck underneath. Didn't think too much of it, until I was underneath one day doing an oil change. I started looking at all the heat shields and they appeared to be tight. I took out the rubber mallet and started tapping on the driver side cat, nothing. Got to the passenger side and I'm hearing a lot of rattling. Fast forward to last year, while driving I'm getting a "
nails in a coffee can" like sound while driving. I've spoken to a few shops, each one quoting about 700-850 to replace the cats + y pipe. It seems like most of the cost is from the labor involved. Every shop I called won't cut/install a universal one, and said its better just to stick with a new setup.

I did some searching, and I'm assuming the removal/installation is near identical to the TBSS. Removing 8 bolts, the support for the transmission, put a jack under the tranny to keep it in place and then break/torch off the existing bolts leading to the headers. So I'm figuring roughly 4 hours to swap it out, unless there's a better way of doing it?


Found a kit on Rock Auto by EASTERN CATALYTIC (part #50418) for $250-ish shipped, comes with a 5 year/50k warranty and has the gaskets/clamps included. Pricing doesn't seem to bad, I did toy around with the idea of just going cat-less for more fun/cheaper cost, but unfortunately Indiana won't deem it legal unless its 25+ years old. There's a pick n' pull near me with a ton of 03-06 Yukon/Tahoes/Silverados etc and they're selling the cats + y pipe for under $150. If I wanted to go the extreme cheapskate route, would it be a direct fit from the full size trucks into this platform? I don't have a problem paying more for the new kit, but I was curious to see if it technically "doable".
 

aaserv

Member
Dec 1, 2019
408
N of Baton Rouge, La.
Helluva price...jump on it. I see that same setup elsewhere for over $500. Researching Eastern Cats it seems as though most/all are not bolt on and youll need to weld it in...
Saving $100 might be tempting but id be worried about 1 not designed for your car flowing more or less thus setting off the ck eng light
 
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Mike534x

Original poster
Member
Apr 9, 2012
894
Helluva price...jump on it. I see that same setup elsewhere for over $500. Researching Eastern Cats it seems as though most/all are not bolt on and youll need to weld it in...
Saving $100 might be tempting but id be worried about 1 not designed for your car flowing more or less thus setting off the ck eng light

My concern were the cats not fitting/lining up with the exhaust flange if I snagged one off a full size truck. I'm still debating, the downside with this cheap kit is that it isn't stainless steal, which isn't a total deal breaker but having to worry about the assembly rusting out is another concern. The kits off RockAuto are pretty much bolt in, no welding required unless I go for a "universal" cat, which seem to be hit/miss depending on the brand and whatnot. Though its weird the cat isn't triggering a CEL despite the innards rattling around.
 

Drec

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Jan 29, 2018
216
Yakima, Washington
Are you getting a code set, with a cat failure? If you aren’t, it’s probably a muffler instead of a cat; which is what is wrong with mine.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Are you getting a code set, with a cat failure? If you aren’t, it’s probably a muffler instead of a cat; which is what is wrong with mine.

Not necessarily. Whatever is left of the honeycomb may still be working enough to not trigger a cat performance code. Hearing rattling in the cat is a pretty definitive indication.
 
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Mike534x

Original poster
Member
Apr 9, 2012
894
Are you getting a code set, with a cat failure? If you aren’t, it’s probably a muffler instead of a cat; which is what is wrong with mine.

Nope, there hasn't been any codes set. I had one for the upstream O2 sensor on the driver's side last Fall that I changed out as well as the passenger side. The muffler is only 2 years old, but this has existed before it was changed out.

Not necessarily. Whatever is left of the honeycomb may still be working enough to not trigger a cat performance code. Hearing rattling in the cat is a pretty definitive indication.

Passenger side definitely has a rattle when tapping on it, and I have noticed that there is a slight noticeable loss in power especially when merging.
 

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