Strange shift sound after tune
Thread Starter
Instructor
Joined: Jul 2015
Posts: 177
Likes: 12
From: Allen Texas
Strange shift sound after tune
I just got put on American long tube headers with CAI and a tune on my 2017 Z06. When I'm in Sport or Track mode (the loudest exhaust mode) I hear a strange sound when shifting gears normally, not WOT. I can only describe it like a sneeze!
I didn't get a trans tune. Is this the exhaust opening up as it shifts? Has anyone else experienced this? If so, any way around it?
I like (sometimes) being able to go into stealth mode with the exhaust, but I've noticed that when I back off on the peddle to cruise, it closes the exhaust. NO! I want it open while on the road. I don't have headers to sneak around down the street. I think I want it wide open ALL the time. I guess I need to forgo the electronic system and install a manual NPP. I haven't upgraded the exhaust yet. I used to have on my C6 headers and Corsa Extremes. That combo was nice. I had no NPP on the C6. What do you suggest for the C7?
I didn't get a trans tune. Is this the exhaust opening up as it shifts? Has anyone else experienced this? If so, any way around it?
I like (sometimes) being able to go into stealth mode with the exhaust, but I've noticed that when I back off on the peddle to cruise, it closes the exhaust. NO! I want it open while on the road. I don't have headers to sneak around down the street. I think I want it wide open ALL the time. I guess I need to forgo the electronic system and install a manual NPP. I haven't upgraded the exhaust yet. I used to have on my C6 headers and Corsa Extremes. That combo was nice. I had no NPP on the C6. What do you suggest for the C7?
Thread Starter
Instructor
Joined: Jul 2015
Posts: 177
Likes: 12
From: Allen Texas
I ended up pulling the fuse for the NPP system to force the flaps open 100% of the time. Who would want to not hear the loud exhaust, right? So, it actually did help the abruptness of the shifting noise. I guess it was forcing the flaps open, then closed when shifting. That can't be normal. I'm going to keep looking into this, but wanted to give an update and would love to hear if others have the same issue or not.
I will probably invest in the M2W system in case I wanted to make it quieter rolling in at midnight sometimes. Any users of the Mild to Wild switch?
I will probably invest in the M2W system in case I wanted to make it quieter rolling in at midnight sometimes. Any users of the Mild to Wild switch?
Thread Starter
Instructor
Joined: Jul 2015
Posts: 177
Likes: 12
From: Allen Texas
I'm referring to just simple normal driving, not WOT.
It's my understanding that starting in 2017 (my year) GM locked the trans so it makes it harder to do a trans tune.
I didn't do the trans tune because of the added cost. I'll have to check and see what that cost is and also see if it would even fix this issue.
With the flaps wide open now (by pulling the NPP fuse) it does sound some better, but it's still a strange sound. Almost like it's shifting way too early and not power shifting. When I paddle it, I never hear that sound.
It's my understanding that starting in 2017 (my year) GM locked the trans so it makes it harder to do a trans tune.
I didn't do the trans tune because of the added cost. I'll have to check and see what that cost is and also see if it would even fix this issue.
With the flaps wide open now (by pulling the NPP fuse) it does sound some better, but it's still a strange sound. Almost like it's shifting way too early and not power shifting. When I paddle it, I never hear that sound.
Safety Car
Joined: Mar 2004
Posts: 4,048
Likes: 1,478
From: South Florida
You can also tune the NPP so that it is always open in Track mode, mixed in sport and closed in Tour. Then you don't need to buy a M2W system or pull the fuse. I commonly make this change for my remote tuning clients. It does require licensing the vehicles CCM which is 2 credits.
Thread Starter
Instructor
Joined: Jul 2015
Posts: 177
Likes: 12
From: Allen Texas
Always open actually isn't ALWAYS open, flaps will close in higher speed and low rpm. Are you saying that there is another "tune" way to keep the flaps open? Even if there is, I want to be able to close them when I pull into my neighborhood and I can also start the car with flaps always closed as well. The neighbors appreciate that!
And the strange sound before was always there (flaps open or closed). I do have a M2W switch which I LOVE btw. The only thing that fixed the strange noise was the trans tune. Now it's more power tuned with the shift points and the sound I was hearing totally went away.
And the strange sound before was always there (flaps open or closed). I do have a M2W switch which I LOVE btw. The only thing that fixed the strange noise was the trans tune. Now it's more power tuned with the shift points and the sound I was hearing totally went away.
You can also tune the NPP so that it is always open in Track mode, mixed in sport and closed in Tour. Then you don't need to buy a M2W system or pull the fuse. I commonly make this change for my remote tuning clients. It does require licensing the vehicles CCM which is 2 credits.
Melting Slicks
Joined: Dec 2007
Posts: 2,902
Likes: 668
From: North Fulton Georgia
I just got put on American long tube headers with CAI and a tune on my 2017 Z06. When I'm in Sport or Track mode (the loudest exhaust mode) I hear a strange sound when shifting gears normally, not WOT. I can only describe it like a sneeze!
I didn't get a trans tune. Is this the exhaust opening up as it shifts? Has anyone else experienced this? If so, any way around it?
I like (sometimes) being able to go into stealth mode with the exhaust, but I've noticed that when I back off on the peddle to cruise, it closes the exhaust. NO! I want it open while on the road. I don't have headers to sneak around down the street. I think I want it wide open ALL the time. I guess I need to forgo the electronic system and install a manual NPP. I haven't upgraded the exhaust yet. I used to have on my C6 headers and Corsa Extremes. That combo was nice. I had no NPP on the C6. What do you suggest for the C7?
I didn't get a trans tune. Is this the exhaust opening up as it shifts? Has anyone else experienced this? If so, any way around it?
I like (sometimes) being able to go into stealth mode with the exhaust, but I've noticed that when I back off on the peddle to cruise, it closes the exhaust. NO! I want it open while on the road. I don't have headers to sneak around down the street. I think I want it wide open ALL the time. I guess I need to forgo the electronic system and install a manual NPP. I haven't upgraded the exhaust yet. I used to have on my C6 headers and Corsa Extremes. That combo was nice. I had no NPP on the C6. What do you suggest for the C7?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Safety Car
Joined: Mar 2004
Posts: 4,048
Likes: 1,478
From: South Florida
Always open actually isn't ALWAYS open, flaps will close in higher speed and low rpm. Are you saying that there is another "tune" way to keep the flaps open? Even if there is, I want to be able to close them when I pull into my neighborhood and I can also start the car with flaps always closed as well. The neighbors appreciate that!
And the strange sound before was always there (flaps open or closed). I do have a M2W switch which I LOVE btw. The only thing that fixed the strange noise was the trans tune. Now it's more power tuned with the shift points and the sound I was hearing totally went away.
And the strange sound before was always there (flaps open or closed). I do have a M2W switch which I LOVE btw. The only thing that fixed the strange noise was the trans tune. Now it's more power tuned with the shift points and the sound I was hearing totally went away.
This is EXACTLY what I am saying. There is a computer called the Chassis Control Module that controls the NPP valve functions. HPTuners unlocked the ability to license and tune this computer module a while ago. You can make the Drive Mode/exhaust modes do whatever you want. You can program TRACK mode to NEVER close, I do for many of the clients that install headers. You can make Sport Mode keep the valves open all the way until 6th gear or not. It is completely customizable.
You can also turn off rumble mode when you start the car to keep the valves closed. Personally I just switch it over to Tour Mode before I start the car if I want to keep it quiet. But to each their own. I don't want to deal with another device to control my NPP since I can just make it do whatever I want in the tune.
