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How important is that support brace that's just behind the end of the cat converter downtubes? After installing my SLP Loudmouth, that has caused a nerve-racking rattling noise. I took the brace off and you can see where it was being worn down into the bare metal. I put a bead of high-temp silicone on the bare spots and let it dry. I put it back together and the rattling was gone, but a vibration still existed.

I removed the bar completely and it all disappeared. Just how important is this support brace? I'm wondering if I can just leave it off. I would believe so since the exhaust uses the OEM rubber hangers.
 

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When I had the R/T exhaust installed on my SXT, I had the same problem with the exhaust rattling on that brace. I took it back to the installers and they tightened-up the front and now the rattle is gone. Get yours checked.

That brace is there as a "safety feature" in case the exhaust breaks at the front. It prevents the pipe from hitting the ground while you're moving, causing it to spear up through the car into the back seat. (... so they say...)

I've also head of some people cutting off an old piece of tire and fastening it around that brace to stop the rattle. Not my first choice...
 

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Remove the brace, then put in a wooden spacer, about an inch or so thick, underneath the x-pipe, and put the brace back in. Adjust the exhaust and tighten, remove brace, then wooden spacer, put the brace back on. You should now have clearence between the two.
 

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Yep

Remove the brace, then put in a wooden spacer, about an inch or so thick, underneath the x-pipe, and put the brace back in. Adjust the exhaust and tighten, remove brace, then wooden spacer, put the brace back on. You should now have clearence between the two.
This is the right call - I had to do this twice retorquing my clamps to get it to stay off the brace. I used a 2x3" scrap of 3/4 thick plywood. When I removed the wood after tightening it left 1/2" of clearance and has never touched again.

I think allowing it to touch is bad news - transfers heat into the floorpan as well as any movement the drivetrain makes.
 

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When I had my Mopar/Borla system installed, the muffler shop noticed that the support was up against the system and gained clearance by adding a large nut at6 each mounting point (4) between the support and the floorpan. For the most part it worked, but on some "combination" bumps, there would still be some momentary contact. I managed to iron almost all of it out by adding a thin washer to each "spacer". I think that this method is safer than using any of the abovementioned materials - considering the temp of the exhaust system.
 

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I fixed an exhaust rattle and gained 40 HP!! Here's how...
On my '95 Camaro, the exhaust pipe routing over the rear axel is VERY tight stock, adding an aftermarket catback with the larger pipe diameter caused a intermittant (sp?) rattle. I dyno'd the car and found that the computer was pulling 10-12 degrees of timing, but only sometimes. I finally figured out the knock sensor was "hearing" the exhaust rattle and mistaking it for engine knock. So...the moral of the story is ALWAYS make sure you have enough clearance for your exhaust. I've learned since then that this is actually a somewhat common problem, modern knock sensors are extremely sensitive. Maybe our sensors on the LX cars are more sophisticated, and can tell the difference between a rattle and actual knock, but why take the chance? I had a rattle on the Charger after installing the Borla 125's, back near the rear axle. It just takes a little more time and patience to do it right, but it's worth it.
 

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This is the easy way in my book and it's still going strong on my charger. I had the same problem with my corsa exhaust and then added 4 washers (purchased at walmart) to each bolt and then put the brace back on and i now have at least 1inch clearance. no noise at all since doing that. I also did it without jacking the car up...go me:lol:
 

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I just installed borla cat back and took her for a spin around the block and whoa!!! Really annoying rattle/vibrations! I wish I had read this thread first. Luckily, I noticed that that cross member brace piece was touching one of the pipes. I just grabbed 3 washers and put them on all 4 studs that hold the brace on. I'd say 90% of the rattles are gone but there's still one vibration at a certain rpm and still some rattles over really really bad bumps. I'm going to have a new brace welded for me that has a curve to it so the pipes can't hit it and put it on this week. I just don't love using the spacers/washers because it's still not enough clearance on a big pothole (I'm in ny and we have huge potholes).
 
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