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The only time mine ever chirped was switching from V4 to V8.

It was a Single Chirp and could happen at any speed.

This noise in the video comes on after some time and if you are on the gas the flapper will be open as the extra exhaust gas force keeps it open under V8 and throttle.

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4 minutes ago, Sierra Dan said:

The only time mine ever chirped was switching from V4 to V8.

It was a Single Chirp and could happen at any speed.

This noise in the video comes on after some time and if you are on the gas the flapper will be open as the extra exhaust gas force keeps it open under V8 and throttle.

There aren't many things on a truck that can make that noise at speed.  Just trying to narrow down places to look that could potentially be it.

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I read some articles about driving in M5 mode and tried that.  Same problem though.  My next step is to try wiring/clamping the valve open to see if that works.  I agree that it is good to eliminate possibilities...  It seems like it is something motor/exhaust related as it fluctuates in correlation with stepping on the gas pedal and letting off of it.  It's not always at 3,000 rpm, but that seems like the hot spot.  As you could hear it slows down immediately after letting off the gas pedal.  Picks right back up when I hit it again. 

 

Stupid question....., but is "chirp" the right word to describe that sound?

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My truck was making a “chirping” noise and noticed it when it was in v4/v8 mode transition... clamped the valve open.. noise gone.

 

i agree with the other guys, something cheap and easy to narrow down

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11 hours ago, Music Junkie said:

I read some articles about driving in M5 mode and tried that.  Same problem though.  My next step is to try wiring/clamping the valve open to see if that works.  I agree that it is good to eliminate possibilities...  It seems like it is something motor/exhaust related as it fluctuates in correlation with stepping on the gas pedal and letting off of it.  It's not always at 3,000 rpm, but that seems like the hot spot.  As you could hear it slows down immediately after letting off the gas pedal.  Picks right back up when I hit it again. 

 

Stupid question....., but is "chirp" the right word to describe that sound?

From what I can hear in the videos, yes, 'chirping' would be an accurate description.

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Well, I wired the little valve open and took it for a test drive......  No go....  :sigh:

 

I wish I had some rollers to put the back end on.  That way I could put it under load and open the hood to see if I could get a better grip o where the sound is coming from.  It's hard to tell while driving down the road.  Back to the drawing board.

 

Any other ideas of things to check?

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That sure sounds like a pulley to me... any belt debris in that area?

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14 hours ago, Racindave said:

That sure sounds like a pulley to me... any belt debris in that area?

Pulley was my first thought.  Right before I received the truck ad new water pump and tensioner pulley were put on.  When I got it, I fixed the brakes and have been working on this problem since.  I took it into a repair shop and they said it was the alternator and they wanted $690 for a new alternator and serpentine belt.  I bought a new alternator (AC Delco) and a new serpentine belt for under $300 and changed it out in about 30min or so.  I was hoping that was going to fix it, but it was a no go.  That is why I came here.  I was hoping someone else had gone through this and could help out.  The hard part is that I can't get a great sound clip, and even if I could, it is hard to tell where it is coming from.  I am going to try and have my buddy stand outside and I am going to drive by him and see if he can get a sound clip that is any clearer.  Also, maybe he will be able to identify more closely where it might be coming from.  It could be the AC pump.....  I tried turning the AC off, but it still makes the sound.  That rules out the clutch (I think).  It could still be the pulley.  I used a stethoscope to try and hear if one of the pulleys was bad, but to be honest, there is a lot of noise in there as it does have high mileage.  Also, I am not very well versed in what I should be hearing or not hearing when it comes to that. 

 

 

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Does it have an idler pulley? Might be a cheap stab in the dark. From what i hear  I would almost put money on it being a pulley. 

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1 hour ago, Racindave said:

Does it have an idler pulley? Might be a cheap stab in the dark. From what i hear  I would almost put money on it being a pulley. 

Is the idler pulley the same as the tension pulley?  Sorry for my ignorance....  It looks like the serpentine belt goes around the main engine pulley, the water pump pulley, the tension pulley and the alternator pulley.

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Like I said last week, take the belts off and drive. If there's no noise it's on the accessory drive. Pretty simple.

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1 hour ago, Lsgun1 said:

Like I said last week, take the belts off and drive. If there's no noise it's on the accessory drive. Pretty simple.

I am very nervous about doing that.  Considering this engine has 219K miles on it and that I need to get it up to 3,000-4,000 rpm under load to get the noise to start.  I have heard that even running them around the block without the belts can pop a gasket or warp a head.  Especially with the aluminum components.  Back when they were cast iron it was a different story.  Maybe I am worrying too much about that......  If you have done it, and others have too, maybe it's not as big a deal as I am imagining....

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You have a temp gauge, watch it. You shouldn't need more than 5 minutes to figure it out.

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On 6/27/2019 at 2:50 PM, Darmichar said:

That sounds like it could be the flapper valve oscillating with the exhaust.  I'd clamp it open and drive the truck and see if it stops making the noise.

Yep. Same issue took me awhile to figure out.

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