Knocking/Rattling

[Rojoryu]

Knocking/Rattling with Vid

I purchased my company vehicle from my employer, a 2007 Yukon SLT with 206k miles on it. A few weeks ago it started knocking under mild acceleration but only for the first few minutes after startup. The past few days it has started doing this when warm and it's getting progressively worse. If I rev it in park it will make the same noise as it decelerates but it's more of a rattle then. It doesn't make any noises at idle and if you hammer on it while driving it accelerates fine with no noises. Had the oil changed today with no change after another 30 miles.

The noise seems to be coming from the bell housing area but it's difficult to pin down. Definitely seems louder on the passenger side. I have searched this forum and the interwebs extensively and it points to a cracked flexplate. I feel like if it was motor related I would have power loss and it would not clear up under heavy acceleration.

Any input would be greatly appreciated. I was really hopping to get another year out of this vehicle.

Thanks

 

[sick1166]

cat converter or loose exhaust

 

[Rojoryu]

cat converter or loose exhaust

I hope it's not motor/transmission related. I looked as good as I could and couldn't find any loose exhaust parts. If a cat was dead wouldn't it throw a code? When I get home tonight Im going to look at the plate. I have a feeling even through the inspection window it could be difficult to determine if that's the problem. Any tests I can do to confirm or rule it out?

 

[Rojoryu]

Here is a vid I took today. I had my wife rev while I listened. At first I couldn't tell if the noise was coming from the Bell housing or the passenger side cat but once I spent a minute under there it seems pretty obvious it's the cat. If so what now? Just buy a replacement, pull one from a junk yard? Is there anything I can do to quite this one down?

https://www.youtube.com/watch?v=ZQmpndA9PTg

 

[sick1166]

how I know is its common and just happened to me thought it was tranny at first.then realized it was the cat I went to several muffler shops and got quotes anywhere from $600.00 - 1200.00 stopped by a slow shop one day guy said he would do both for 200.00 so I did it same one as yours drove with mine for a year got better milage with a bad cat but then the noise was embarrassing and I found a cheap shop

 

[Christoph559]

I had the same deal with mine thought the bottom end was letting go. I hit the converter with a mallet and it rattled like crazy. Here in CA it cost 275 per side

 

[Rojoryu]

Thanks for the replies. You guys got a shop to cut the bad one out and weld a good one in? The shops around here (NC) are telling me I have to buy the whole assembly (both cats and wye pipe). I found a few assemblies for $250 and a flow master for $350. Looks pretty simple to bolt on.

 

[Gzes]

Should just be cat. To make it cheaper just cut off yourself order a cat and just have hem weld it in. That's what I did before I bought my welder and only paid $50 for getting welded