V4 to V8 driveability issues.

[alcarames]

Hello all! I'm new here. While I've owned several GM SUV's, they were purchased used. Back in January 2016 I purchased a left over 2015 GMC sierra SLT with the Z71 package in irridium gray. Beautiful truck, and got a great deal on it.

 

After several hundred miles I noticed almost a stutter around certain speeds and that would result in a loud clunk coming from the driveshaft. i brought my truck in to the dealer to have this issue looked at. I was even able to duplicate the noise and vibration for the tech in a test drive. I was told this is normal. How the hell is a new vehicle stuttering and clunking normal?

 

I noticed I can see when it's in V8 mode and V4 mode so I watch and the noise and vibration usually when in V4 mode and switching into V8 mode. I'm also usually at part throttle when this is happening. Any fixes for this other than voiding my warranty by getting an aftermarket tuner?

[salem185]

For the same reason I returned my 2015 Silverado High country which done only 2600 KM and get the 2016 model.

 

Look for bulletin #PI1354C: Information on Vibration Analysis and Diagnostic - (Aug 14, 2015)

Subject: Information on Vibration Analysis and Diagnostic

Models: 2014 Chevrolet Silverado 1500, 2015 Chevrolet Silverado 1500, 2014 GMC Sierra 1500,

2015 GMC Sierra 1500.

[Newell33]

The V4 to V8 programming on my 2014 was horrible,just like yours. There are several threads on this. Google Range Devise and you'll find somewhat of a solution. My solution was trading for something different.

[Icecreman]

I'm don't know about 15's but it's completely seamless on my '16. I can't tell it's switching unless I look at the DIC. Hope you get it resolved.

[14silverado4.3]

Funny, at dealer for same shudder feel from V4 to V6. No codes were found.

 

Told to not watch for it on the DIC screen, drive a little different.

 

Their advice, if you want to make it happen - you can but don't try to make it happen.

 

Oh, if there are no codes they can't fix it.

[tnchevy]

My 2014 is not noticeable at all when going from 4 to 8 cylinder mode. The only thing I feel is when the transmission shifts down a gear which is usually when I am V4 but have to give it more gas so it switches to V8 at the same time it is down shifting.

[5Horizons]

Unless I am looking at the display, it is almost imperceptible. I thought it was gonna bother me, but unless I'm looking for it, I don't feel it. I guess they got it worked out for 2016.

[Sean Demura]

Never had an issue on my 4.3 '15

[gmckenzie]

I could notice the switch from V8 to V4. Felt like the motor was lugging. Started running mid-grade fuel and find I notice it a lot less. Other option is to drive in M5. I would do that around town where I would never get into 6th gear anyway. Locked out the V4 mode completely.

[diyer2]

Try driving with the trans in M5 or M7 to keep it out of V4 and see if it makes a difference.

[[email protected]]

I purchased a 2016 GMC sierra and I thought I was going to hate the AFM but it is seemless in this model year. I cannot tell when it is in v4 mode without looking at the display. I also noticed that it drops out of v4 mode almost immediately when the slightest throttle is applied. The earlier versions were likely staying in v4 mode longer and causing weird harmonics under part throttle conditions. This makes me think that GM could reflash the system to eliminate your problem. Unfortunately I believe they compensated on the 2016 models by holding it in a higher gear longer in an effort to keep rpm's as low as possible. Occasionally I come out of a curve and attempt to accelerate lightly and there is an audible drone as the engine labors in far too high of a gear. I initially thought it was the AFM but its not. Its in v8 mode it simply in too high of a gear. Frustrating. They are trying to accomplish too much with overly complex programming in an effort to comply with Federal emissions and mileage standards. I know for a fact that a custom tune would remedy 95% of these driveability issues but I dont want to void my warranty on a $45K truck. I got the 6.2L with 8speed and it actually runs strong at full throttle. Its the other 99% of the time that its a confused garbled mess trying to eek the last ounce of gas out of every gallon that drives me nutty.

[toro1966]

I purchased a 2016 GMC sierra and I thought I was going to hate the AFM but it is seemless in this model year. I cannot tell when it is in v4 mode without looking at the display. I also noticed that it drops out of v4 mode almost immediately when the slightest throttle is applied. The earlier versions were likely staying in v4 mode longer and causing weird harmonics under part throttle conditions. This makes me think that GM could reflash the system to eliminate your problem. Unfortunately I believe they compensated on the 2016 models by holding it in a higher gear longer in an effort to keep rpm's as low as possible. Occasionally I come out of a curve and attempt to accelerate lightly and there is an audible drone as the engine labors in far too high of a gear. I initially thought it was the AFM but its not. Its in v8 mode it simply in too high of a gear. Frustrating. They are trying to accomplish too much with overly complex programming in an effort to comply with Federal emissions and mileage standards. I know for a fact that a custom tune would remedy 95% of these driveability issues but I dont want to void my warranty on a $45K truck. I got the 6.2L with 8speed and it actually runs strong at full throttle. Its the other 99% of the time that its a confused garbled mess trying to eek the last ounce of gas out of every gallon that drives me nutty.

 

+1 on my 2015. Seamless. I am as retentive as they come and it is imperceptible.

[Britt Lifsey]

Only know my 2015 is in v4 based on DIC.

[OldBlue61]

^ Same.

[Z45]

Don't let it get to you. You are not driving a truck you are driving a computer.