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Old 06-04-2021, 07:56 PM
soupman soupman is offline
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Default Exhaust drone or rearend noise

I am trying to diagnose a noise on my car and think itís a drone noise. I never had a car that had a drone so not exactly sure what it sounds like. This is a humming noise only when cruising between 2100-2400rpm. The frequency goes up and down, like a seesawing noise. Itís continuous up/down frequency. I donít think itís the rearend because the frequency does go up down, I think a rearend growl would be continuous at the same frequency but wanted to ask some opinions.

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Old 06-05-2021, 12:17 AM
PontiacJim1959 PontiacJim1959 is offline
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Muffler type? I used DynoMax years ago and they had a very noticeable/audible drone right at the RPM range you are getting. Below 2,000 and above about 2,300 the drone was gone. I believe that has been cured with later designs, but that was a common complaint with them years ago.

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Old 06-05-2021, 09:08 AM
soupman soupman is offline
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This is a 3” system that does not have mufflers, only 2 resonators of unknown brand. They are installed right past the rearend, but I don’t have tailpipes on yet. It is pretty load, but trying to rule out the rearend first.

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Old 06-05-2021, 11:27 AM
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Chris65LeMans Chris65LeMans is offline
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It doesnít make sense to me that the rear end would make noise only in a certain engine RPM range.

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Old 06-05-2021, 11:37 AM
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padgett padgett is offline
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Quite common, are called "harmonics". A lot also depends on whether the exhaust tip is under the car or a little past the bumper. Finally do you have an X or H pipe ? They dramatically change frequencies.

I've run cars before with no mufflers and just resonators or cats by always carry the tip out the back or the side.

BTW you do have rubber hangers ? Solid hangers can also be noisy. In other words, too many unmentioned variables.

ps have had glass packs & RA headers on mine for many years. I like the sound but has been known to set off car alarms.

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Old 06-05-2021, 12:34 PM
soupman soupman is offline
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The tips end near back of trunk, I need about 10” to get them past the rear bumper. I do have rubber mounts. I agree if rearend would hear it all the time most likely. Maybe I should put some tailpipes on it, I wonder if would change the frequencies?

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Old 06-05-2021, 12:39 PM
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Getting past the bumper would keep the trunk floor from resonating. Do you have a trunk carpet ?

Can see where the tips are on mine, it does not drone.

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Old 06-06-2021, 09:25 AM
soupman soupman is offline
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I do have trunk carpet. I can get a built in resonator tailpipe with turndowns, I wonder if that would help. Do you guys think this could be the rear? Seems to me years ago I had a whine from a rearend and it was always there just got progressively loader the fast I went.

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