Strange rattle: Engine, transmission, or high flow cats?

[Demon Coyote]

Hi all,

Just noticed a strange rattle that's coming from underneath the car. Not sure what's causing the noise or where exactly it's coming from at the moment. It happens a little bit after a cold start. When I start driving the car the noise is gone and I won't hear it again until I start it again when everything has cooled down again. I can't figure out where the noise is coming from, because obviously when you want someone else to hear it, it never shows up. This only happens after the car has been sitting for a while and everything has cooled down.

After driving it and during driving I won't hear anything, even when I park up again and let it idle. I thought it might be a heat shield, but it wasn't after I checked and also I got my exhaust tightened again just in case something was loose. However, it still makes the noise most of the time. I had to change my engine oil and was changing my trans and diff oil anyways, so I thought maybe that would help, but it's still the same.

I've attached a video of what it sounds like and would love to hear some feedback or if anyone else is experiencing something like this.

Here is the link to video:
https://drive.google.com/open?id=0B0ZNhBEpzRH5bTAwYU51TUNCSm8

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[Chris5.0coyote]

Have you guy found any thing out I have a 2018 gt base model and it started making a kinda loud ticking / knocking on the bottom end on the passenger side on cold starts and as soon as the cars warmed up and I drive it it’ll be there very quiet then after about 5 mins of driving I get out and check for the noise and it’s gone it only stays there when it cold or whenever I don’t start the car for more than a couple hours it’s really bothering I only have 3700 miles on the car right now and the noise started around 2900 miles scared to take my car in because I don’t want it to be in the shop for months because I’ve heard someone’s car has been on back order because of a clutch and transmission internals for 5 months also my brothers a technician at Chevy and he put it on the lift he thinks it’s coming from my trans cause when he drives it he hears the rattle between 1800rpm-2300rpm then stop anywhere above that Sorry for the long message just trying to explain myself aswell as I can also a friend told me he thinks it could be because of my cats but doesn’t really make sense cause cause when I give it gas it’ll tick / rattle / knock whatever the noise it it’ll keep going until it’s warmed up then it’ll stop when the cars warm and won’t make any noise but when I start it again after it sitting for a while it’ll come back again till it warms up

 

[Demon Coyote]

Have you guy found any thing out I have a 2018 gt base model and it started making a kinda loud ticking / knocking on the bottom end on the passenger side on cold starts and as soon as the cars warmed up and I drive it it’ll be there very quiet then after about 5 mins of driving I get out and check for the noise and it’s gone it only stays there when it cold or whenever I don’t start the car for more than a couple hours it’s really bothering I only have 3700 miles on the car right now and the noise started around 2900 miles scared to take my car in because I don’t want it to be in the shop for months because I’ve heard someone’s car has been on back order because of a clutch and transmission internals for 5 months also my brothers a technician at Chevy and he put it on the lift he thinks it’s coming from my trans cause when he drives it he hears the rattle between 1800rpm-2300rpm then stop anywhere above that Sorry for the long message just trying to explain myself aswell as I can also a friend told me he thinks it could be because of my cats but doesn’t really make sense cause cause when I give it gas it’ll tick / rattle / knock whatever the noise it it’ll keep going until it’s warmed up then it’ll stop when the cars warm and won’t make any noise but when I start it again after it sitting for a while it’ll come back again till it warms up

I just got my new clutch installed and the shop had to take the exhaust off. I asked them to inspect my high flow cats and it turned out the cats were fine. I asked them to torque everything down and also to tighten up the exhaust clamps too. So far the noise has not come back when I do a cold start. Also, the guys at the shop said the could not replicate the sound/noise I was describing when they did a cold start and let it sit for a while trying to listen as well.

There was speculation that it could be the pressure plate or one of the other clutch components. At this point I'm not sure what caused the noise, just hoping it never comes back and if it does then we'll know it's not related to the trans.

 

[Chris5.0coyote]

How has everything been since then ? Was all the parts they changed under warranty?

 

[Demon Coyote]

How has everything been since then ? Was all the parts they changed under warranty?

It's been good ever since no noise came back. I can't point out exactly what it is that cause the problem since the clutch, flywheel, driveshaft, pilot bearing, and throw out bearing were all changed. Also the exhaust was taken off and retightened again. There was no noise I heard after that but it seems like one of those things was the problem. No this was not done under warranty, this is an upgrade from stock to a twin disk clutch that I asked a performance shop to do.

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