V4 to V8 Squeak During Shift

[jmitchell]

I'm just at around 3,000 miles and have incredibly sensitive ears. Even the slightest creaks or squeaks inside or outside the vehicle have my nerves on edge.

Recently (within the last week) I have noticed a slight squeak or chirp sound (very short and quick sound) from the right rear of the vehicle somewhere near the exhaust. I am always driving so I haven't had time to get back there and pin point it with someone else behind the wheel. It definitely seems like its coming from somewhere near the right rear wheel or exhaust. It occurs when the gas is applied just after coasting (right at the start of the short lag time after applying the gas pedal). It does not occur when starting from a full stop nor does it occur during normal up-shifting during acceleration. The only time it seems to occur is when the V4 kicks over to V8 mode as I can see it on the DIC (from coasting to accelerating again).

Does anyone have any thoughts as to what is causing this? Is there an extreme differential in air pressure that is sent through the exhaust manifold when going from V4 to V8 that could be creating this sound? Something in the exhaust or is it non-exhaust related?

Thanks in advance for the help.

 

[Steve1081]

Check the emergency brake line and see if it is rubbing on the sway bar end link.

You will see what I am talking about if you crawl under there.

I had the same exact thing after I lowered mine and that was what was making the noise. There is a bracket there to hold it off that you can remove and adjust.

 

[jmitchell]

I had that issue on week one. Something sounded crunchy coming from the left rear side (drivers side). That would occur every time I applied the brakes or went over speed bumps at low speeds. I could duplicate that noise by flexing the car up and down even with the vehicle turned off. As you said that one was the e brake cables that were rubbing. I did some taping, moving, and zip tying of the cables to solve that one.

This issue/noise however sounds more like a metal chirp or squeak that is light and quick. Definitely coming from the right rear (passenger side) near the exhaust and I can't duplicate the sound when the vehicle is off. Seems like it is tied to the V4 transitioning to V8 mode. Only time it happens. Any other thoughts?

 

[jmitchell]

I thought I would share this solution that I found from another forum (GM-Trucks.com). Make sure to follow the link in this thread to a separate longer thread with pictures. We all have this valve on the 2015's and I'm clamping mine open tonight!

V4 to V8 Squeak

Another good link...
Passive Exhaust Valve

**Update: I put a standard 2" to 3" hose clamp on this to keep it open similar to the links above and the squeak has gone away. The exhaust even sounds a little meatier in the V4 mode. (no difference in V8) It's as simple as turning the valve 90° counter-clockwise and clamping...that's it.

 

[jmitchell]

Also to add to this, I don't notice as much throttle lag as I did prior to clamping the valve open. Maybe it is just a mental thing but it seems to be running quicker.

 

[twhitechurch]

THANK YOU!!! It was driving me nuts! And no one believed me either. I'm swapping out the exhaust soon but until then this is great!

 

[jmitchell]

Yes it was very annoying...glad the information helped. I now have 2 hose clamp fixes for misc. issues. Still better than dealer investigating the problems.

 

[Tylus]

are there any drawbacks from pinning this check valve open?

 

[TheAgency]

I also locked my exhaust "Flapper" valve open, no problems here. I used 2 hose clamps and so far no problems at all. My main motivation for doing so was the exhaust note on startup; the 5.3 in my 15' Yukon sounded weak compared to the previous generation, and especially compared to my 6.0 in my previous Avalanche.

Now it sounds great with a really tight and clean growl; like the engine that just started really knows what it's doing. More along the lines of my buddy's highly modified S4 in lieu of a '90s Silverado with straight pipes and Nascar stickers.

 

[Lt. Steve]

Second exhaust-same problem in 2015 Tahoe

Yes I too had the squeak during acceleration. Was told the problem was a rusted piece in the exhaust. Yes, RUSTED! Of course that sounded crazy to me for a brand new truck. Anyway, dealer replaced the exhaust and squeak disappeared. Now, 2 months later, squeak has returned although not as bad. Dealer called GM and they said not to replace exhaust again because problem will eventually keep coming back. They are aware of problem and said it is a design issue. Now what do I do? This is my third Tahoe (08, 11 & now 15)and I just can't believe it. Are we just supposed to put up with this issue on a $50k vehicle?