New exhaust rattle

[Moneypit62]

I've searched everywhere and can't seem to find a thread that helps me. This is my first post too so hopefully have the right section.

I bought and installed a 3.0" DPE catback on my VF2 LS3 Auto over the weekend. I finished bolting it up in my garage but there was a metallic rattle coming from the cat area on first start up.

I got back under the car and found I needed to tighten the bolts a bit more and this reduced the rattle.. I then went for a test drive and felt some pretty bad vibrations through the body of the car. I found that after tightening the cat flange bolts up more, the connecting pipe lifted and was now contacting a bolt under the trans.

I was told that the system came with all bolts and gaskets required.. And when I unbolted the stock system there was no gasket between the cats and midsection? I assumed this was normal and didn't put a gasket in there originally, but I have now. I can tighten the bolts up and it doesn't lift up and contact the body, but it still rattles.

Is it normal for there to be no flange gasket on the cats, and is a bit of rattle normal for a new exhaust system until it's been driven for a bit?

 

[15SUPERSPORT]

I've searched everywhere and can't seem to find a thread that helps me. This is my first post too so hopefully have the right section.

I bought and installed a 3.0" DPE catback on my VF2 LS3 Auto over the weekend. I finished bolting it up in my garage but there was a metallic rattle coming from the cat area on first start up.

I got back under the car and found I needed to tighten the bolts a bit more and this reduced the rattle.. I then went for a test drive and felt some pretty bad vibrations through the body of the car. I found that after tightening the cat flange bolts up more, the connecting pipe lifted and was now contacting a bolt under the trans.

I was told that the system came with all bolts and gaskets required.. And when I unbolted the stock system there was no gasket between the cats and midsection? I assumed this was normal and didn't put a gasket in there originally, but I have now. I can tighten the bolts up and it doesn't lift up and contact the body, but it still rattles.

Is it normal for there to be no flange gasket on the cats, and is a bit of rattle normal for a new exhaust system until it's been driven for a bit?

You may check to see if the system is contacting the trans tunnel crossmember under the car. You may also have a heat shield dancing around. Good luck!

 

[Moneypit62]

You may check to see if the system is contacting the trans tunnel crossmember under the car. You may also have a heat shield dancing around. Good luck!

The tunnel cross member is no longer on as it won't fit over the new hot dogs. I'll have to check heat shields but I never touched them and didn't have this sound with the stock system?

 

[15SUPERSPORT]

The tunnel cross member is no longer on as it won't fit over the new hot dogs. I'll have to check heat shields but I never touched them and didn't have this sound with the stock system?

That's unfortunate. If you can get it up on stands you may be able to give it a listen while someone taps the throttle a bit until you find the rattle. As for the tunnel brace, you may consider the Halo tunnel brace for the 5th gen Camaro. Direct bolt in, extra clearance, nice piece.

 

[Moneypit62]

That's unfortunate. If you can get it up on stands you may be able to give it a listen while someone taps the throttle a bit until you find the rattle. As for the tunnel brace, you may consider the Halo tunnel brace for the 5th gen Camaro. Direct bolt in, extra clearance, nice piece.

View attachment 223704

Thanks for that, I'll definitely look into that piece as it was next on my list after I sorted this rattle haha

As for heat shields on the cats, I've just gone under and taken them off for today so I can see if the rattle goes away. I'm hopeful but also skeptical hahaha

 

[Not_An_Abba_Fan]

The cat flanges have a cone type gasket that has to be removed so that a flat gasket can be fitted. If you have left the cone gaskets on there, then you will have all sorts of dramas getting the system to line up.

 

[Moneypit62]

The cat flanges have a cone type gasket that has to be removed so that a flat gasket can be fitted. If you have left the cone gaskets on there, then you will have all sorts of dramas getting the system to line up.

That makes complete sense.. But I was told that it was a bolt up system that required no modifications. Is there any way of making this work without going to a workshop?
I assume you're saying the cone needs to be cut off both pieces and a flat flange welded in?

 

[Not_An_Abba_Fan]

That makes complete sense.. But I was told that it was a bolt up system that required no modifications. Is there any way of making this work without going to a workshop?
I assume you're saying the cone needs to be cut off both pieces and a flat flange welded in?

No, it's just a gasket. Get a screwdriver and lever it off. It will be tight, you may have to hit the screwdriver with a hammer to get it between the gasket and the flange.

 

[Not_An_Abba_Fan]

Get a screwdriver in there.

 

[Moneypit62]

Get a screwdriver in there.

View attachment 223716

I'll need to take a photo to show you as mine don't look like that. The flange on the cat has about 30mm of straight pipe sticking out from the flange. The connecting pipe I was sold has a cone shape that fits over this with a "floating flange" (not sure on technical name but will make sense when I get a photo).

I think the issue is that this "floating flange" doesn't actually meet up with the cat flange and form a nice seal.