[ReFLeX135]

I know the exhaust is kinda loud (fuse is pulled because of the rattle) but there is a grinding type noise right at the V4 to V8 change. This sound occurs louder usually, but this day it was hard to get it on video. You will most likely need headphones to hear this.

I think it occurs when I down shift too (not in the video), but that's not at all what's happening here. If anything in the video it's shifting up at the same time. I do hear a different grinding when the gears drop in low speeds. That'll have to be a different video another day.

GM and dealer are giving me a hard time so I'm trying to get as much evidence as I can.

(Edit) Newest Video:


Original post's video:

[HCGxKaLiBeR]

Do you mean the noise from 0:08 - 0:14?

I think thats the AFM vale closing/opening sound. My car has the same sound, very annoying.

[ReFLeX135]

Originally Posted by HCGxKaLiBeR

Do you mean the noise from 0:10 - 0:14?

I think thats the AFM vale closing/opening sound. My car has the same sound, very annoying.

Yeah I repeat the sound/video a few times and it occurs in the video at 8s, 10s, 12s etc. I was thinking it was the valves too, but can reproduce it sometimes and hear almost the same sound when I cruise at 30, slow down, down shift like normal like the auto would but in manual mode into 3rd, and then 2nd while coming to a stop. Maybe it's the valves opening too?

[HCGxKaLiBeR]

I hear it whenever it changes V4 to V8 or vice versa.
Still noticeable when cruising on highway with both windows up.

I have the fuse pulled as well. Before the exhaust flapper would mask the noise.

[Glen e]

Killl the afm with a range module.

Google range afm

[raptor5244]

I assume you are pulsing the gas to get it in and out of V4 mode in that video? I have my fuse pulled but I don't really hear anything during the change. I do get a different (lower) exhaust note with the fuse pulled when the auto is in 7th or 8th gear before it downshifts. This is when the NPP usually has the rear valves closed so you would get a different tone. Unfortunately, the different tone for me and many others is a NPP buzz/rattle.

[HCGxKaLiBeR]

Originally Posted by Glen e

Killl the afm with a range module.

Google range afm

I don't really mind the AFM system. I actually have better MPG than my I6 BMW...

However, I don't know the sound is from here or not. If so, I would really like to know how to force it open...



Picture from: http://www.camaro6.com/forums/showthread.php?t=423058

[ReFLeX135]

Originally Posted by raptor5244

I assume you are pulsing the gas to get it in and out of V4 mode in that video? I have my fuse pulled but I don't really hear anything during the change. I do get a different (lower) exhaust note with the fuse pulled when the auto is in 7th or 8th gear before it downshifts. This is when the NPP usually has the rear valves closed so you would get a different tone. Unfortunately, the different tone for me and many others is a NPP buzz/rattle.

No I was not pulsing the throttle. I casually get up to speed, about 25 mph area, and when I get around 25 and begin to almost hold that speed this screech happens. The sound I hear isn't the tone or cut off of exhaust or a quieter sound, it's a metal scratch or grind type sound.

[raptor5244]

Originally Posted by HCGxKaLiBeR

I don't really mind the AFM system. I actually have better MPG than my I6 BMW...

However, I don't know the sound is from here or not. If so, I would really like to know how to force it open...



Picture from: http://www.camaro6.com/forums/showthread.php?t=423058

Those are the AFM NPP valves. A8 trans cars get two sets of NPP valves, for forward pair after for AFM and the rear set to control the exhaust volume. M6 cars do not have AFM so they only have the rear set of NPP valves.

When the engine is in V8 mode the AFM valves are open, when you go into the V4 mode they close. The reason why we need AFM vales is because the exhaust note in V4 mode is horrible. So, you really don't want to force those NPP valves open unless you are disabling AFM along with it.

The GEN5 L99 auto trans cars didn't even have NPP as an option and this is why, no NPP AFM valves. The LS3 M6 cars didn't have AFM so they had the NPP option.

There are two options, you can buy a Range device for a couple hundred bucks that plugs into your OBD port and basically disables AFM v4 mode and in turn keeps the valves open all the time. These have been known to cause CELs from time to time... The other option is to tune the car, which is the cleanest way of doing it but you will lose your warranty at that point. You could also pull the AFM NPP fuse but again it will sound terrible when it goes into v4 mode.

[raptor5244]

Originally Posted by ReFLeX135

No I was not pulsing the throttle. I casually get up to speed, about 25 mph area, and when I get around 25 and begin to almost hold that speed this screech happens. The sound I hear isn't the tone or cut off of exhaust or a quieter sound, it's a metal scratch or grind type sound.

I couldn't hear a screech but I heard the exhaust note change. based on your description though it sounds like the AFM NPP valve is probably the culprit. There is a TSB to spray some DRY Slide lubricant into the front and rear NPP valve assemblies to stop the NPP squeak, which is different from the NPP rattle.

This thread has a copy of the TSB

http://www.camaro6.com/forums/showthread.php?t=442728

[HCGxKaLiBeR]

Originally Posted by raptor5244

Those are the AFM NPP valves. A8 trans cars get two sets of NPP valves, for forward pair after for AFM and the rear set to control the exhaust volume. M6 cars do not have AFM so they only have the rear set of NPP valves.

When the engine is in V8 mode the AFM valves are open, when you go into the V4 mode they close. The reason why we need AFM vales is because the exhaust note in V4 mode is horrible. So, you really don't want to force those NPP valves open unless you are disabling AFM along with it.

The GEN5 L99 auto trans cars didn't even have NPP as an option and this is why, no NPP AFM valves. The LS3 M6 cars didn't have AFM so they had the NPP option.

There are two options, you can buy a Range device for a couple hundred bucks that plugs into your OBD port and basically disables AFM v4 mode and in turn keeps the valves open all the time. These have been known to cause CELs from time to time... The other option is to tune the car, which is the cleanest way of doing it but you will lose your warranty at that point.

I have another post(zero reply) that I think these are causing weird ticking sound in V4 mode. This is why I would like to disable it but keep the AFM feature.

http://www.camaro6.com/forums/showthread.php?t=456712

I think I will bring it to the dealer and have them to take a look. Apply epoxy to it, lubricate it and whatnot. As long as the noise is gone then I'm happy.

[ReFLeX135]

Thank you all so much for the information here. That 15 facts thread and the images are great. I now remember that TSB for "#16-NA-003: Chirp, Squeak Noise from Rear of Vehicle" but I felt my sound seemed like it was coming from the front of the car. Is there a TSB for the AFM valves?

I'll try go get a better capture of the screech sound. I should be able to hear it from outside the vehicle.

[raptor5244]

Originally Posted by ReFLeX135

Thank you all so much for the information here. That 15 facts thread and the images are great. I now remember that TSB for "#16-NA-003: Chirp, Squeak Noise from Rear of Vehicle" but I felt my sound seemed like it was coming from the front of the car. Is there a TSB for the AFM valves?

I'll try go get a better capture of the screech sound. I should be able to hear it from outside the vehicle.

Well, the AFM valves only close in v4 mode when you are moving. Gonna be hard to capture that sound outside the car. In the pics you will see they spray that lube in both the front AFM valves and rear valves. They look like the same part, just another set for the automatics. .

[HCGxKaLiBeR]

Originally Posted by ReFLeX135

Thank you all so much for the information here. That 15 facts thread and the images are great. I now remember that TSB for "#16-NA-003: Chirp, Squeak Noise from Rear of Vehicle" but I felt my sound seemed like it was coming from the front of the car. Is there a TSB for the AFM valves?

I'll try go get a better capture of the screech sound. I should be able to hear it from outside the vehicle.

Brought my car into the service for oil change today. There are quite a few TSBs on the 2016 camaro. One of them something about Left side rattle/ticking/knocking noise, generated from the fuel line pluse. Too bad the tech dept. is closed on Sat, I will need to bring it over on work days to have them check it again.