Swooshing sound?

[Graham26ZR2]

My 21 gmc 1500 3.0 was totaled and I replaced it with a 26 1500 ZR2 3.0. I have a swooshing sound under the passenger seat area under the truck at times. I did notice an electronic valve in the exhaust in that area that looks like the flapper valve on the gas trucks. Could this be restricting exhaust and causing this noise? If so any tips to keep it open?

 

[Graham26ZR2]

My 21 gmc 1500 3.0 was totaled and I replaced it with a 26 1500 ZR2 3.0. I have a swooshing sound under the passenger seat area under the truck at times. I did notice an electronic valve in the exhaust in that area that looks like the flapper valve on the gas trucks. Could this be restricting exhaust and causing this noise? If so any tips to keep it open?

Tried to post a short video but keep getting the oops something went wrong error message

 

[MO_ZR2]

Not sure exactly what you’re seeing but the 3.0 has a valve that looks kind of like the valve on gas trucks with cylinder deactivation to reduce drone and improve exhaust sound when using varying cylinders. On the diesel however it’s a bit more complicated.
It helps with engine braking when in Tow/Haul mode, the valve closes to restrict exhaust flow, which increases backpressure to assist the transmission in slowing the truck down

Also, it helps the motor reach operating temperatures more quickly and I’m sure has emission implications (like DPF regens, etc) - I suspect removing it could throw codes. Might do some google work.

And it may not even be your sound at al? but I would start at the dealer to see if they can isolate the sound before deleting the flap valve personally. There are at least a couple guys on here that work on these and have way more hands on knowledge and might be able to chime in (and correct anything I might be off base on)

 

[Graham26ZR2]

Not sure exactly what you’re seeing but the 3.0 has a valve that looks kind of like the valve on gas trucks with cylinder deactivation to reduce drone and improve exhaust sound when using varying cylinders. On the diesel however it’s a bit more complicated.
It helps with engine braking when in Tow/Haul mode, the valve closes to restrict exhaust flow, which increases backpressure to assist the transmission in slowing the truck down

Also, it helps the motor reach operating temperatures more quickly and I’m sure has emission implications (like DPF regens, etc) - I suspect removing it could throw codes. Might do some google work.

And it may not even be your sound at al? but I would start at the dealer to see if they can isolate the sound before deleting the flap valve personally. There are at least a couple guys on here that work on these and have way more hands on knowledge and might be able to chime in (and correct anything I might be off base on)

Patiently waiting for a GM tech to reply

 

[GatorZR2]

My 21 gmc 1500 3.0 was totaled and I replaced it with a 26 1500 ZR2 3.0. I have a swooshing sound under the passenger seat area under the truck at times. I did notice an electronic valve in the exhaust in that area that looks like the flapper valve on the gas trucks. Could this be restricting exhaust and causing this noise? If so any tips to keep it open?

Babymax swoosh is totally normal. Lm2 and LZ0 use a Garrett variable geometry turbocharger which does not use a waste gate. Boost and drive pressure are electronically controlled. LZ0 turbocharger got an internal upgrade along with exhaust emission redesign. So that may explain why you hear the swoosh a little more on the LZ0 than the LM2. I heard the swoosh when I first got my truck, now with my upgrades I really hear it and can actually hear turbo spool. If you start hearing a squeak or rattle in that area then definitely get it checked out.

 

[Duramax Joe]

Patiently waiting for a GM tech to reply

I know I am late to the party but yeah that valve is the source of the swoosh sound you are hearing. The valve is a back pressure control valve and the actuator that controls it is called an exhaust gas recirculation actuator. GM named them but anyway the valve controls back pressure in the exhaust to help with egr flow and to help to egt faster on cold starts. The reason for the noise is the shaft on the valve has no gasket so exhaust escapes by it some more than others due to the shaft fitting tighter in some than others. I have noticed some barely make a noise at all and some only do it till they warm up and some are just really bad all the time. Mine only does it till it warms up.

 

[Graham26ZR2]

Thanks for the replies everyone!