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My guess is that this is not a transmission issue. This is your engine coming out of the 4 cylinder deactivation mode (what GM calls AFM, or "Active Fuel Management".

Here's how to find out....
On your driver information center, set your display to show Instant MPG. It should also say "V8" right next to it. Drive around with it set that way for a while, and watch what happens. You will see that at low speed and low torque situations, the truck will go into 4 cylinder mode which shows as "V4" on the display. The vibration you feel is a slight lugging of the engine, before all 8 cylinders come back on. It does not do it under harder acceleration, because the AFM won't come on when there is a need for more power. You should be able to feel the lugging, and as soon as it stops, your display will show "V8" again.

The way to avoid this around town is to dhift into Manual (like the old "low" gear on most automatic transmissions). In manual, you can shift gears manually, or set it at a predetermined gear. If you use any gear M1 through M5, the AFM will not activate, and you will not feel that lugging.

Hope this helps! It's annoying, but your dealer is right...there is nothing wrong with the truck. It takes a while for the truck to learn your driving habits. Once you get 5,000 miles or so on the truck, you won't even notice it anymore.

 

Thanks for the quick response, I'll check that out. Just started doing it though, after 10,000 miles. Great forum!

 

I have the exact same problem . My truck is a 2011 Silverado CC with the 5.3 and approx 7,000 miles on the clock , but where my issue is a bit different is when i'm at 1100 rpms there is a bad vibration in the IP Dash , this is very , very annoying and is driving me nuts . So not only is the AFM kicking in and out at this RPM range ( 1000-1500rpms ) and making the engine feel sluggish , but now i have this bloody interior vibration to deal with !! Had it in for service and got the same story , nothing they can do ...its the AFM and you have to live with it !! . I will be taking it back and have them rip the dash out to fix the vibration .

 

Yes, I know. I started watching it and it did it when it was in V4 mode, so its normal. but I can see where the vibration wil start to cause things in the dash to start to come loose and rattle a bit. good luck

 

FYI........

Note the use of the term "slight vibration".

TSB 06-06-05-001C

"Some customers may comment in a change in the exhaust note or tone when an Active Fuel Management System equipped engine is in 3 or 4 cylinder mode. Some drivers may also notice a very slight vibration in either the accelerator pedal, floor pan, and/or the steering wheel. This is a normal condition for Active Fuel Management System equipped vehicles and no repairs should be attempted."

Customer Information on Active Fuel Management

When the Active Fuel Management System is enabled, physical changes take place within the engine that allow it to run as a 3 or 4 cylinder motor with accompanying additional fuel savings. The change in exhaust tone is expected as all sound from the exhaust is the result of combustion in the engine. The ability to perceive these changes in sound are kept to very minimal levels as the Active Fuel Management System is only activated during a steady state/near steady state driving or during coast down. In both of these situations, the load on the engine is minimal and general exhaust volume (sound) is low. You may give a copy of this bulletin to your customer

&#PIP4371A

 

I notice these vibes and symptoms as well...I just picked up a '11 Silverado 1500 Extended Cab LT and have put 1000 miles on it in a week. Like anything else I think it will not be a factor the more that I drive the truck. I do a 100 miles per day almost 99% highway. Avg just under 19 mpg right now but expect that to go up once engine is fully broken in.

 

My guess is that this is not a transmission issue. This is your engine coming out of the 4 cylinder deactivation mode (what GM calls AFM, or "Active Fuel Management"....Hope this helps! It's annoying, but your dealer is right...there is nothing wrong with the truck. It takes a while for the truck to learn your driving habits. Once you get 5,000 miles or so on the truck, you won't even notice it anymore.

My presumption is that your guess is ludicrous and you're not qualified to diagnosis his vehicle problems. I have the exact issue as the original poster. Even though I joined this forum previously, I found his post using a Google search. Putting the truck into manual doesn't solve anything and there are still rumbles. Whatever vibrations AMF may cause are completely different than what's happening as he described it IMHO.

I'm bringing my truck in for more service and I'm around 99% positive they'll find a problem with it. I would advise the original poster to do the same... I'll let all of you know what they find. At the current rate my new Silverado is having problems GM might have to deal with me in court under state lemon laws. :evil:

 

EKinMN doesn't post "ludicrous" things, and is highly qualified to answer any question on GM trucks. He has over 3000 posts on this site, and not one of them was a waste of time. As a personal friend of his, I must tell you that your "presumption" is wrong. I don't want to scare you off, but since you're a newer member, I think it's best to warn you now about saying such things.

Yes, I know. I started watching it and it did it when it was in V4 mode, so its normal.

According to the OP, EKinMN nailed the answer. This has been a widely discussed topic- driveline vibrations when the newer 5.3L engines go from V8 to V4 mode, or vice-versa. While I can't help your dissatisfaction with your truck, I hope that you and the dealer are able to sort things out.

 

..According to the OP, EKinMN nailed the answer. This has been a widely discussed topic- driveline vibrations when the newer 5.3L engines go from V8 to V4 mode, or vice-versa. While I can't help your dissatisfaction with your truck, I hope that you and the dealer are able to sort things out.

Whatever... Does GM give you a new truck discount for being a die hard fanboy or something? I suppose my truck just started to sound like I'm driving on the shoulder after 1k miles because I'm an @!#$ing idiot and didn't notice it right off the bat. :roll: The truck still makes the rumble strip noise in manual shift, so maybe you can diagnosis that.

Or better yet, I'll let ASE master mechanic diagnosis it tomorrow.

 

Dude, chill. Sorry that you may have bought a lemon, but the people on this forum didn't sell it to you. Read and maybe you will learn something.......... hopefully some respect.

 

My guess is that this is not a transmission issue. This is your engine coming out of the 4 cylinder deactivation mode (what GM calls AFM, or "Active Fuel Management"....Hope this helps! It's annoying, but your dealer is right...there is nothing wrong with the truck. It takes a while for the truck to learn your driving habits. Once you get 5,000 miles or so on the truck, you won't even notice it anymore.

My presumption is that your guess is ludicrous and you're not qualified to diagnosis his vehicle problems. I have the exact issue as the original poster. Even though I joined this forum previously, I found his post using a Google search. Putting the truck into manual doesn't solve anything and there are still rumbles. Whatever vibrations AMF may cause are completely different than what's happening as he described it IMHO.

I'm bringing my truck in for more service and I'm around 99% positive they'll find a problem with it. I would advise the original poster to do the same... I'll let all of you know what they find. At the current rate my new Silverado is having problems GM might have to deal with me in court under state lemon laws. :evil:

Social media (internet forums) work like this--you post a problem, and people give opinions to you for FREE. Yup--free advice! We are not (all) mechanics. We reply based on what we have experienced or heard from others. The "wisdom of the masses" is often right, and often faster than one single "expert" (like a mechanic at your dealership).
If you don't like the replies you get, you are free to do (almost) whatever you want with the advice. The one thing you WILL NOT do, to me or any other member of this site, is discount their ideas, or make fun of them. This is a fantastic well intentioned group of people, who are often right, even though they are guessing at issues over the INTERNET, and can not even see or hear your vehicle's problem.

Good luck with your problem. Sorry my advice was not helpful to you.

 

Let me know what the dealer says. Like i said, mine didnt start this until about 9500 miles. It does this when in V4 mode, or going in and out of V4 mode. Now it seems to go into V4 mode much more than before hence more vibration noticed. If you disconnect the batt. does that reset the learning transmission? It shifts into 6th gear much earlier than when it was new, so I'm not pressing the throttle as hard and this may be causing it to go into V4 mode more oftern than when it was new. Just wondering if your trucks are doing the same.

 

I get the vibration...I think it is just the nature of the beast with these 5.3L AFM editions

 

I bought a 2011 GMC Sierra with the 5.3 V8 with the Z60 Suspension,I now have 1300 miles on it and never have heard any transmission noises,felt any jerking or vibrations up to now,I had a 2006 Tundra that when coming to a fast stop,you would feel like the truck was being pushed from behind about 5 seconds after stopping.

I'm not a mechanic or pretend to be one,but it may not happen on all 6 speed GM trucks,mine sure handles perfect and compared to the Tundra,this GMC is a real truck.

Robert

 

I have a 2011 with the 5.3 and a 6 speed i have about 8800 miles on it and the only time i ever notice the v4 mode is sometimes when it goes back to v8 you can feel the power pick back up but i have never had any vibrations so far it has run just fine

 

Well those 2 answers just threw a wrench into the works lol Great

 

Haha maybe people just have 2 different meanings of what the think a vibration feels like like i said mine just feels like you hit the gas ou can feel more force against you

 

If you want to get out of the V4 mode to stop the vibration and or lugging of the engine, an ever so slight tap on the gas pedal will wake up the other 4 cylinders. That's what I do when I feel the it's time for all 8 to be firing.

 

The one thing you WILL NOT do, to me or any other member of this site, is discount their ideas, or make fun of them...

My point of contention or frustration is when someone states they're having problems, and keeps getting generic replies about AFM or that it's operating as designed... AND ISN'T EVEN TOLD TO HAVE IT CHECKED OUT AT THE DEALER

I have my truck back now. It had the torque converter replaced in it. The rumble is gone along with shuddering that happened under load. I can post more details later when I have the work documentation in front of me.

My truck has under 2000 miles on it and has had the transfer case and torque converter replaced thus far... If I hadn't been headstrong and opinionated I'm sure I could easily buy in to the ideas some forum members are posting about it being AFM or normal behavior.

:|

 

The tap the skinny pedal post was only sent as a tool that could help identify a problem, by using this simple method one can get the truck out of the V4 mode, once running on all 8 if the noise and vibration still exists the symptoms being cause by the AFM would be eliminated by allowing you to verify if your issue was actually being caused by V4 mode? Remember there is no such thing as a stupid question only stupid answers. :?

 

To each their own this site is and will always be helpfuL to someone but not to everyone and there are certified people on this site that can be helpful to us.

 

I have noticed that it is in the V4 mode when the slight rumble occurs. Sounds like everyone elses does this also so I'll assume that this is normal I guess this helps the mpg a little. One post on here stated that he had the dealer turn off the V4 mode and his mileage didnt change. I'll leave mine be. I can average 18.5 mpg if I feather the throttle and stay below 75 mph. This is far better than the other brands of trucks my friends have, Ford or Toyota.

 

after i installed my m.i.t. and drop in filter I could really hear this. Oh well turn up the tunes.

 

i have the same vibration problem caused by the active fuel management. by putting your tranny in manual 5th gear, it deactivates the afm, but by raising your rpm's your fuel economy will suffer slightly

 

I'll be getting an In-Tune tuner when I return from deployment if for nothing else to turn off the AFM. I hate that %$#@ vibration.