2018 Sierra 5.3 high pitch whistle or whine at idle

[79Mercy]

Hey guys and gals, new member, purchased my 2018 GMC Sierra Z71 5.3 6-speed new  off the lot a few months back.  Been doing lots of reading on here, lots of good info on here so thanks for that! 

 

Anyways, over the past few thousand miles i have noticed 3 things that kind of bother me, otherwise i love the truck.  When the truck is sitting idle in park i can hear a fairly loud high pitched whistle or whine noise from the engine if i'am standing outside the truck in front of the radiator.  Sounds like a cricket or dog whistle almost, but doesnt stay steady, it changes pitch and goes away if engine is raced.  It seems to be only when the truck has warmed up, i dont notice it after a cold start.  Seems loudest new the alternator, maybe whine from alt or pulley, small vacuum leak, not sure really?  

 

My other two concerns are a hard downshift when slowing down quickly, it shifts down from 3-2 pretty hard at times, also the v4/v8 flap valve on the exhaust rattles loudly when at idle.

 

I stopped by the dealer i purchased it from and expressed my concerns with the service manager, he heard the high pitch whine or whistle noise, but said he'd never heard that noise before, and he said he wasnt even sure if they would be able to repair with, which kind of make me question their ability.  He heard the rattle from exhaust valve, and ordered a new exhaust, he said they would try and look into the high pitched noise when i return to have exhaust installed.  As for the hard downshift he stated this was normal and nothing could be done about this, basically stated they all did it, normal operation.  

 

Has anyone hear experienced a high pitched noise similar to what i described above? Anyone had any success getting that 3-2 downshift smoothed out on the 6 speed, lots of info on the 8 speed, not so much for the 6 from what i can tell? 

 

Thanks!

[Racindave]

Is your air filter canister sealed good? If not that may be your whistle....

Edited June 10, 2019 by Racindave

[Paintor]

I think you hold down the “Tow-Haul” button for 7 seconds to disable “Grade Braking” and stop the downshifting issue.

 

 

[1SLOW1500]

I hate the tow down shift but maybe it works in towing a heavy load. The trans can be fixed with a tune. 

My experience with he noise you hear is the power steering pump. I'm not saying that is your issue on a brand you truck. 

In tune you could and should remove v4 mod also then no exhaust valve noise issues.  

I know this may not be what you want to hear but if a service manager or any service man started by saying he didn't think they can fix a issue I would walk out and go somewhere else.  Waste of time and they write a service ticket to you vin. 

[silveradosid]

there is no power steering pump on it

[TRKLGND]

Your power steering is electric and a tune can completely void your power-train warranty.

[79Mercy]

Just wanted to give an update to this high pitch whistle noise i was having, the dealership found it was in fact the alternator, that fixed the issue i was having after they installed a new one.  Thanks for the input 

[Chevy19]

On 6/15/2019 at 7:59 PM, 79Mercy said:

Just wanted to give an update to this high pitch whistle noise i was having, the dealership found it was in fact the alternator, that fixed the issue i was having after they installed a new one.  Thanks for the input 

Did your whistle noise sound like this? I’m having a whistle on my 2019 Sliverado 1500 5.3 V8 .. any input would be appreciated. Thanks!

 

[79Mercy]

On 2/11/2020 at 5:55 AM, Chevy19 said:

Did your whistle noise sound like this? I’m having a whistle on my 2019 Sliverado 1500 5.3 V8 .. any input would be appreciated. Thanks!

 

Yes, thats the exact noise my truck was making, hasnt come back since they replaced the alternator 

[Chevy19]

3 minutes ago, 79Mercy said:

Yes, thats the exact noise my truck was making, hasnt come back since they replaced the alternator 

Okay, they are replacing the alternator next week! Hope this does it! Thank you for the reply. Did this mess with your lights at all?

Edited February 13, 2020 by Chevy19

[79Mercy]

1 minute ago, Chevy19 said:

Okay, they are replacing the alternator next week! Hope this does it! Thank you for the reply. Did this miss with your lights at all?

No it didn't mess with any lighting or electrical systems that i could tell.  Mine literally only made that noise at hot idle in park or neutral, drop it in gear or race the engine the noise went away.  

[Denise Moody]

I've had my truck since 2017 and they said it was the fuel pump and replaced it, but just recently when I took my truck in for service, I noticed that they had on the paperwork they had replaced water pump, any ways it still does the cricket sound and when I took road trip, I noticed a very loud screeching sound. Thought maybe it had something to do with using the cruise control? At one time it made this noise when I was slowly coming to a stop and my lights/dash came on.

[Aj443]

I have the same issue with the whistle noise but mine goes away when I turn the lights off and only does it when the lights are on it drives me nuts (2018 1500 5.3)

[TravStu]

Hey guys, Im experiencing a similar issue on my 17' Sierra but it's not a whistle.

I hear a soft whine in idle, when accelerating in 1st and 2nd gear, and when I slow down to come to a stop. I don't really hear it after 2nd gear but it definitely gets louder when I hit the gas in low gears.

 

I bought an AFM disabler thinking that was possibly the issue but am still having the same noise.

 

I had a 5.3 in my 2013 Silverado and never heard this whine so I guess that's why I notice it so much with this truck.

Transmission fluid is good and full.

 

I've read a ton of forums and it sounds like it could be the fuel pump, water pump, or "normal" as some mechanics have told people. 

 

Any advice or help would be great to ease my mind or point me in the right direction.

 

Thanks