L99 exhaust rattle any help - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

2003chevy · 07-17-2009, 06:02 PM

well it started i wanted to make it louder than the weak stock exhaust sound so i figured like any other car you buy an aftermarket and away you go. Little did i know and only after installing it did i realize how annoying this 4 cyl. mode is and then i read a couple of threads that others have had an issue with changing the exhaust on an L99. So question is do i get rid of the giant resonater in the middle or do i get it tuned so this mode does not come on?
I bought just the axel back street series magnaflow and it sounds great over 2000 rpm but when your driving normal anything under that makes a rattle sound not heard before changing the stock exhaust.
Any insight is helpful just wondering if anyone has an L99 with the catback street series if there experiencing the same problem.

*CamaroSpike23* · 07-17-2009, 06:10 PM

if you pull the resonator, chances are the 4cyl mode sound will be more apparent. as for tuning out the 4cyl mode, how much do you really want it?

as for the rattle, is it just while moving or while stationary as well? you might have part of the exhaust rubbing under the car.

2003chevy · 07-17-2009, 06:29 PM

Quote:

Originally Posted by CamaroSpike23

if you pull the resonator, chances are the 4cyl mode sound will be more apparent. as for tuning out the 4cyl mode, how much do you really want it?

as for the rattle, is it just while moving or while stationary as well? you might have part of the exhaust rubbing under the car.

when its cold or just started it does it a little but when it shifts a bunch of times and going about 30 or 35 in 4th gear at about 1100 rpm its really boggy sounding.

2003chevy · 07-17-2009, 06:43 PM

Quote:

Originally Posted by CamaroSpike23

if you pull the resonator, chances are the 4cyl mode sound will be more apparent. as for tuning out the 4cyl mode, how much do you really want it?

as for the rattle, is it just while moving or while stationary as well? you might have part of the exhaust rubbing under the car.

Another thing is i have been under the car and the exhaust is laying on a cross member with 4 bolts to the frame that the exhaust is touching but besides that support there are only two mounts in the very back where the exhaust is on rubber mounts but it is very tight and barely moves an inch or so.

*CamaroSpike23* · 07-17-2009, 08:06 PM

Quote:

Originally Posted by 2003chevy

Another thing is i have been under the car and the exhaust is laying on a cross member with 4 bolts to the frame that the exhaust is touching but besides that support there are only two mounts in the very back where the exhaust is on rubber mounts but it is very tight and barely moves an inch or so.

which crossmember is it? is it just a sheetmetal piece to help support the exhaust or is it a structural component? can you get a pic of it? or (if its just a sheetmetal piece to help support the exhaust, pull it off and drive around real quick to see if that is the problem?

edog · 07-17-2009, 08:18 PM

When you are driving at the low speeds you can use the manual mode and keep the revs up by staying in a lower gear.

I did not go aftermarket, I just cut the exhaust off and had customer pipes installed from axle back. Mine is an l99, and I understand what you are saying as well. I turn the radio on and put it at a comfortable level. It does not bother me. I like hearing the exhaust. You could also put the exhaust back on if it is really getting to you.

BOBSS · 07-24-2009, 02:46 AM

I have an aftermarket exhaust that is hitting this cross member and it's driving me nuts.
I'm thinking up a device to put between the tubes and the cross member to prevent contact. A different cross member would be nice too

Name: contact.jpg
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Name: contact.jpg
Views: 807
Size: 111.8 KB

camaro1 · 07-24-2009, 07:52 AM

the resonator is probly broken inside, mine also started to rattle bad so i cut the bottom off of it and found a large baffle broke loose inside so mine came off and i had a custom stainless x-pipe made

*mlee* · 07-24-2009, 08:21 AM

Quote:

Originally Posted by 2003chevy

when its cold or just started it does it a little but when it shifts a bunch of times and going about 30 or 35 in 4th gear at about 1100 rpm its really boggy sounding.

That boggy sound is just AFM. I have a full catback that came with resonator so it's not much of a problem, except just knowing when AFM kicks in.

AFM is probably causing some extra vibraton that could be contributing to your problem.

07-17-2009, 06:02 PM	#1
2003chevy Drives: 2003 avalanche 2001 friebird Join Date: Mar 2009 Location: Waukesha Wi Posts: 25 View My Garage	L99 exhaust rattle any help well it started i wanted to make it louder than the weak stock exhaust sound so i figured like any other car you buy an aftermarket and away you go. Little did i know and only after installing it did i realize how annoying this 4 cyl. mode is and then i read a couple of threads that others have had an issue with changing the exhaust on an L99. So question is do i get rid of the giant resonater in the middle or do i get it tuned so this mode does not come on? I bought just the axel back street series magnaflow and it sounds great over 2000 rpm but when your driving normal anything under that makes a rattle sound not heard before changing the stock exhaust. Any insight is helpful just wondering if anyone has an L99 with the catback street series if there experiencing the same problem.

07-17-2009, 08:18 PM	#6
edog Drives: 2010 2SS/RS IOM Join Date: Oct 2008 Location: F'BURG VA Posts: 3,832 View My Garage	When you are driving at the low speeds you can use the manual mode and keep the revs up by staying in a lower gear. I did not go aftermarket, I just cut the exhaust off and had customer pipes installed from axle back. Mine is an l99, and I understand what you are saying as well. I turn the radio on and put it at a comfortable level. It does not bother me. I like hearing the exhaust. You could also put the exhaust back on if it is really getting to you. __________________ Update...Build in process, Forged Rods, Pistons and rings, Johnson Lifters, NOVI1500 ECS SC, 13lb boost or more, LS3 Conversion 114/228/241 COMP CAM, Frostbite 4 row Aluminum radiator, 6L80 built, Circle D 6L80 PRO SERIES MULTI 258MM 2D, Stock 3.45 gears, 1-7/8 American Racing Headers w/HF cat, X-Pipe, Lingenfelter dual fuel pump, E-85 flex sensor, ATI super damper pulley, Ported TB, 160 therm, Trans cooler, Pedder's sways/end links/sub frame bushings, BMR trailing arms & toe rods, Coil overs. HP/TQ pending

07-24-2009, 07:52 AM	#8
camaro1 Drives: 550+RWHP 2010 camaro Join Date: Sep 2007 Location: wisconsin Posts: 1,588	the resonator is probly broken inside, mine also started to rattle bad so i cut the bottom off of it and found a large baffle broke loose inside so mine came off and i had a custom stainless x-pipe made __________________ 415ci stroker, TVS 2300 Magnacharger, cnc heads, cam, yank ss3200 converter, Kooks long tubes, Bwoody true cold air kit, ZL1 Pump, magnaflow 3" cat-back, lowering springs,BMR control arms and tie rod bars, 3.73 gears, diff mounts, RX can, ADM fuel controller

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07-24-2009, 02:46 AM	#7
BOBSS Outlaw Drives: 2010SS Join Date: Jan 2009 Location: Mooresville NC Posts: 299	I have an aftermarket exhaust that is hitting this cross member and it's driving me nuts. I'm thinking up a device to put between the tubes and the cross member to prevent contact. A different cross member would be nice too