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Hello guys, my lbz has always made a whine noise when I am decelerating. If I give it any throttle the noise goes away. Only modification is a cold air intake.

Possibly the turbo???
Thanks for any opinions
 

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Discussion Starter #3
Over 100 views and nothing but cricket's? Mabey I should switch sites? I've had bad luck here! I'm on a fishing forum that is awesome lots of responses and activity. It makes me check and respond to the site multiple times a day!!!
 

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Whine upon decel doesn't really describe it well enough to respond.
When did it start? Ie, if it was always there, wss it before the CAI?
How loud is it?
Does it come from underhood?
Can it be duplicated while parked?
Can you reinstall original intake and retest?
Could be an exhaust leak as decel closes the unison ring in the turbo.
Could be serp belt idler pulley (had some weird sounds there).

Or, as you suggested, maybe another site could help?
 

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If you have black smoke, you don't have enough air. It's as simple as that. My truck lives at 7200 ft, and even with a monster tune, it will not smoke. Part of that's just good tuning. If your truck has mods, that may be the cause. They get really picky when you have intake leaks. You have to look at the whole system as a... Whole. If your mass air flow sensor is bad, it's telling the whole truck that you're getting a lot more air than you are in this case, and that may have been something that got bunged up in the CAI. We can't help you unless you can give us some numbers. How much boost is it producing? Are you able to see if the turbo is actually actuating? What are your EGTs at idle, under load, and coasting? Seems to me like it's maybe stuck somewhere in mid-range boost. It means that you get too much back pressure when you let off the throttle causing that wine, and not enough boost under load, causing the black smoke. You can get the bank's gauge that'll read all the data for around 300 bucks if I remember right. Or you can find an ODB scanner and logger too. you didn't get any responses because you didn't give enough information for anybody to do anything with. I've never once seen the previous poster not have an answer. Except for on this one. Give us some information and we can help you.

As I reread this and try and get rid of typos, I'm reminded that you should probably rig up a way to pressurize the intake and see if you have any leaks. I chased one for 3 years until I finally rigged up a way to pressurize the intake. And sure as hell right at 7 psi there was a leak. I could get 22 lb of boost, but it highway speeds it would whistle and whine.

Sent from my Pixel 3 XL using Tapatalk
 

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Discussion Starter #6
Thanks for the responses, heymccall I bought the truck 3 months ago from my dad and the truck has made the whine on deceleration since I've had it. The noise isn't really loud but it's definitely there. I cant duplicate it while parked once the trucks speed reaches 15mph it goes away. Its sounds like it is coming from under the hood but not positive. I dont have the original intake. I will look for a exhaust leak and check the serpentine belt. Thanks for the ideas

Roswell, there is no black smoke. The only mod is a cold air intake. I dont have a aftermarket gauge to read egt's or other info. The truck runs great other than the whine during deceleration.

Thanks again for the responses and idea's
Dustin
 

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Well sorry, I got my posts mixed up. I've got the same truck with 98k on it. When I was stationed in Japan, my dad had it and the cp3 died due to 'microbes in the biodiesel mix you put in it'. He stopped to fill it up at a truck stop on the way home. They did a horrible job. It was the best shop within 3 hours, but not a good one. You might consider having the oil analyzed at a lab like Horizon. If you do have a shot bearing in the turbo, it should show up since it's cooled with oil. I'm a pilot and we run turbines for hundreds of thousands of hours. But the oil is lab tested. It tells us if anything is starting to fall apart so it can be replaced. Heymccall is an acolyte. He works on all of them, all the time. I'd take his word as gospel. Part of the jet engine guy in me wonders if you don't have some FOD in there somewhere. But as the gentleman said, the idler pullies on the LBZ suck. I've replaced mine twice, and they still like to chirp and whine. It's usually at idle. It might even be the hubs. Major GM weakness in the GMT800s. Both my LBZ and LB7 had issues with them. Might be worth some time on a dyno with the hood open and a buddy so you can isolate the sound. Heck, it could even be driveline related. Next time you hear it, throw it into neutral so there's no engine resistance and see what you hear. We've got a 94 6.5, a 2006, 2007, and a 2008. They all have their own personalities.

Best of luck to ya, and let us know.

Roswell
 

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Hello guys, my lbz has always made a whine noise when I am decelerating. If I give it any throttle the noise goes away. Only modification is a cold air intake.

Possibly the turbo???
Thanks for any opinions
When my factory PS pump gave out at 100k miles, it began to whine pretty loud on decel. Especially when decelerating from cruise speed coming down an off ramp on interstates.
 

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Discussion Starter #10
Thank you gentlemen for the ideas, now I have a few thinks to check.

I did try shifting into neutral during deceleration and it quieted the noise alot when I shift back Into drive the noise is back like normal.
 
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