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Vibration When Afm Puts Truck In 4 Cylinder Mode


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The dealer called me back and said that everything checks out ok on their end. They say there are no codes, etc. being trown. I mean how can a vibration "check out ok"? They are going to contact service assistance or something like that in detroit to see what they have to say. The no codes.....i mean the codes, i think, are only thrown if the computer senses something that is not pre-programmed to happen in the computer?? Can the dealer turn off the AFM?? If Detroit does not have anything good to say, then it is straight to NHTSA, BBB. I think if its normal then its a poor design on GM's part to make a vibration normal characteristic.

It's really hard to tell you what's normal or not without driving your vehicle, understand that. I will repeat though, I

have noticed some weird vibes from AFM engines before when switching back and forth between modes. Nothing severe, like you state your's is, though.

 

Let your dealer work the case. No codes doesn't mean much, there can still be problems. If this is abnormal, when compared to a known good vehicle of the exact same build, then there is something wrong and it CAN be fixed. Be patient. If they can't get it repaired to your liking, contact GM as I stated earlier. NHTSA and the BBB won't do much for you but GM can.

 

 

 

ChevyTech, thanks for all your help and information. I will keep you posted as to what is going on during the process if you don't mind and maybe you can have some insight for me?

 

 

Thanks

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UPDATE!

 

Dealer called me to come pick the truck up. They said they called GM Service Techs in Detroit and they said it is a "normal characteristic" with the truck. I call BS..... I have called GM customer assitance and started a claim with them. The lady was very helpful. The dealer was very nice about everything and said that once GM Techs say its normal that their hands are tied and nothing can be done at the dealer level. After speaking with the Service Manager and Shop Foreman there, I think it all boils down the software issues and poor programming. I think its a combination of the programming in the 6 speed automatic and the AFM. When the truck goes into V4 the cars RPM's always seem to drop and its lugging which I think creates the vibrations. If i put the shifter in manual mode and switch down to 5th or 4th gear it does not vibrate because it downshifts putting V8 mode back into operation. GM is trying to do everything they can do get the most FUEL ECONOMY out of these trucks and don't really care that the customer has to drive a $53,000 truck with a vibration. The service manager did say that if I complain enough that GM will more than likely either come out with a software update to fix problem or they will buy back the truck. We will see what happens next.

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wow, good luck with that. i have say that your vibration is not normal. My 2011 is seamless and i cannot tell when it goes in and out of 4 or 8 cylinders. i get so addicted to watch the DIC, i just smile when i am in v4 and getting 30+ mpg.

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wow, good luck with that. i have say that your vibration is not normal. My 2011 is seamless and i cannot tell when it goes in and out of 4 or 8 cylinders. i get so addicted to watch the DIC, i just smile when i am in v4 and getting 30+ mpg.

 

 

bogeypro, just out of curiosity, does your truck have the 3.42 axle or the 3.08? Mine has the 3.42 and my service manage says that most of the complaints the complaints seem to be with my exact setup.

 

Thanks

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I have a 2010 GMC with 3.42. In 6,500 miles I have not felt any bad V4 vibrations BUT I had a 2008 with 3.73 and it drove me so nuts, I finally traded it away this past spring for 2010. The dealer could not do anything just like your dealer. They showed me some info that said some AFM Engines just exhibit this characteristic and to tell the customer its normal and it a combination of things. The SM agreed (to me at least) it had a vibration that his similar equipped Yukon did not, the tech doing the work failed to see any problem and thought I was just a complainer, I overheard him mention that to the SM when he thought I had left the area.

 

While the dealer claimed they had very few complaints like this, in the meantime I have personally spoken with AFM owners who relate the same thing to me. I have one friend who traded in his 2009 AFM engine for a 6.2L because he claimed it vibrated and they could do nothing to fix it to his liking.

 

All you can do is hold out hope that the more miles you rack up on the truck, the less you will notice this.

Edited by elcamino
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UPDATE!

 

Dealer called me to come pick the truck up. They said they called GM Service Techs in Detroit and they said it is a "normal characteristic" with the truck. I call BS..... I have called GM customer assitance and started a claim with them. The lady was very helpful. The dealer was very nice about everything and said that once GM Techs say its normal that their hands are tied and nothing can be done at the dealer level. After speaking with the Service Manager and Shop Foreman there, I think it all boils down the software issues and poor programming. I think its a combination of the programming in the 6 speed automatic and the AFM. When the truck goes into V4 the cars RPM's always seem to drop and its lugging which I think creates the vibrations. If i put the shifter in manual mode and switch down to 5th or 4th gear it does not vibrate because it downshifts putting V8 mode back into operation. GM is trying to do everything they can do get the most FUEL ECONOMY out of these trucks and don't really care that the customer has to drive a $53,000 truck with a vibration. The service manager did say that if I complain enough that GM will more than likely either come out with a software update to fix problem or they will buy back the truck. We will see what happens next.

I was afraid that is what you'd find. When you shut 4 cylinders down there is going to be a difference in harmonics within the engine that will transfer through the vehicle.

 

The dealer's hands are not tied unless they tied them, themselves. Trust me.

 

Continue working with GM CAC. They will help.

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UPDATE, 12/9/10...

 

I have a case number with GM's Technical Assitance and Brand Quality team. The brand quality team told me on the phone that what I am experiencing is "not normal". I am a little confused now....The dealer provided me with a print out of a bulletin stating it was normal...it's funny that the bulletin was dated 2/23/10 which was before my truck was ever built and does not include my 2011 vehicle year, but the Brand Quality team says its not normal. How can they all not be on the same page on these issues?? Anyway, Brand Quality will be calling my dealer today to discuss with them what can or can't be done to resolve the issue. I would be happy if they would just let me turn the AFM off with a tuner if they would put in writing it would not void my warranty so I can see if its any better. I would think this would be much easier for GM than going through all the motions of a potential buyback.??

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UPDATE, 12/9/10...

 

I have a case number with GM's Technical Assitance and Brand Quality team. The brand quality team told me on the phone that what I am experiencing is "not normal". I am a little confused now....The dealer provided me with a print out of a bulletin stating it was normal...it's funny that the bulletin was dated 2/23/10 which was before my truck was ever built and does not include my 2011 vehicle year, but the Brand Quality team says its not normal. How can they all not be on the same page on these issues?? Anyway, Brand Quality will be calling my dealer today to discuss with them what can or can't be done to resolve the issue. I would be happy if they would just let me turn the AFM off with a tuner if they would put in writing it would not void my warranty so I can see if its any better. I would think this would be much easier for GM than going through all the motions of a potential buyback.??

 

The dealer, alot of times, is not "let in" on what Brand Quality knows. Some dealers are lazy and don't look for the information or look for the wrong information. There is alot of variables, for sure.

 

Sounds like you're on the right track to a solution though. :crazy:

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UPDATE, 12/9/10...

 

I have a case number with GM's Technical Assitance and Brand Quality team. The brand quality team told me on the phone that what I am experiencing is "not normal". I am a little confused now....The dealer provided me with a print out of a bulletin stating it was normal...it's funny that the bulletin was dated 2/23/10 which was before my truck was ever built and does not include my 2011 vehicle year, but the Brand Quality team says its not normal. How can they all not be on the same page on these issues?? Anyway, Brand Quality will be calling my dealer today to discuss with them what can or can't be done to resolve the issue. I would be happy if they would just let me turn the AFM off with a tuner if they would put in writing it would not void my warranty so I can see if its any better. I would think this would be much easier for GM than going through all the motions of a potential buyback.??

 

The dealer, alot of times, is not "let in" on what Brand Quality knows. Some dealers are lazy and don't look for the information or look for the wrong information. There is alot of variables, for sure.

 

Sounds like you're on the right track to a solution though. :crazy:

 

 

 

Thanks ChevyTech, you've been a lot of help so far.

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They can tell you anything on the phone as they are going by your description but its the people that drive it that get to make a decision on whats normal.

 

I had the SM tell me what I was feeling was not normal but the tech's driving and looking for problems said it was normal.

Edited by elcamino
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UPDATE! 12/9/10 230pm Central

 

GM Headquarters called back. Now they are saying "GM is aware of the customer concerns with the vibration and that it is "unfortunately" normal operation" They also said that they are working on find a solution to make the vibration NOT NORMAL OPERATION. I told GM this.....My 2010 Avalanche with same powertrain had no issues at all. I told them that I love the truck but am unhappy at their software and computer programming. All I want is for GM to let me turn off the AFM with no warranty void in which case I want in writing. If they agree and it fixes the issue ( I know it will) then I will leave them alone and keep truck. Otherwise, I will get my cousin who is a federal litigation attorney to represent me free of charge and go for buyback. If they do not answer to this then it is to the media. They are thinking about my request at this time and will get back with me tomorrow or friday. I know that turning the AFM off will not hurt anything. I mean the truck is designed to run on either 4 cylinders or 8 cylinders so why would all 8 cylinders running all the time hurt anything?? Ill keep you all posted

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can you tell if it is an exhaust vibration, have somebody else drive and sit everywhere in the truck, really try to figure out if it is exhaust or drivetrain... i think it's the torque converter, but just a hunch... if you can give a better description of when it does it, what preceeds the vibration and what makes it go away (other than 8 mode)

 

it is possible, especially going down hill to push the gas pedal down ever so slightly and you can gain speed without going into 8 mode, see if it happens at all speeds, under all load conditions in 4 mode. i forget what the load rate is on the engine, 15% load increase causes 8 mode i think, so keep that in mind. also try changing your tire pressures, probably up, i run 45 in the front and 38 in the rears.

 

it would be even better if somebody could get audio on it while your driving with a camera on video or something.

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can you tell if it is an exhaust vibration, have somebody else drive and sit everywhere in the truck, really try to figure out if it is exhaust or drivetrain... i think it's the torque converter, but just a hunch... if you can give a better description of when it does it, what preceeds the vibration and what makes it go away (other than 8 mode)

 

it is possible, especially going down hill to push the gas pedal down ever so slightly and you can gain speed without going into 8 mode, see if it happens at all speeds, under all load conditions in 4 mode. i forget what the load rate is on the engine, 15% load increase causes 8 mode i think, so keep that in mind. also try changing your tire pressures, probably up, i run 45 in the front and 38 in the rears.

 

it would be even better if somebody could get audio on it while your driving with a camera on video or something.

 

I don't think its an exhaust vibration. I can feel it in the gas pedal, steering wheel, and floor. It only happens in V4 mode mainly on level surfaces or while starting an incline. When coasting downhill it does not vibrate or at least I cannot notice it. I think its a combination of the 6 speed tranny being in a high gear at a low speed and in V4 mode....sorta lugging its way along. Nothing makes it go away but going into V8 mode or going down a hill. I am just going to disable AFM as soon as I can get GM to give me the go ahead.

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to me, based on that info, i think it's highly probably that the torque converter is the problem. the engine isn't doing anything different than it would in v8 mode, except 4 cylinders are not firing, therefore a different exhaust note, second order ecoustics are created. the torque converter does momentarily unlock when it goes to 8 mode and i suspect the solenoid or some aspect of the tc is not functioning properly.

 

i guess one other issue could be a lifter not completely compressing.

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  • 4 weeks later...

First, check your state for what the laws are concerning Lemon Laws for vehicles.

Then take it back to the dealer and tell them you purchased a new vehicle that should not have an issue such as a vibration. If the vibration does only occur when in V4 mode, then there is a problem. Any engine should not act differently because of a fuel saving measure. AFM should not make a vehicle vibrate and feel unsafe. Use that term, safety when talking. IT will go a long way. I Lemon Lawed a saturn because of an ignition lock that would stop working and made grinding noises.

 

If you have a law similar to NJ, then after the second time to the dealer write a letter to GM stating your concern. They will most likely schedule a service where a regional rep will look over the vehicle.

 

If the truck did not do this on a test drive or even a similar vehicle, tell the dealer this. And like others have said, make them take you out in similar vehicle on the lot and demonstrate how they do the exact same thing your truck does. If they will not do this, you have your answer about the truck. You can also try talking to the dealership owner. These days, your opinion of a dealer can lead to a lot of lost business and that is the last thing they want.

 

Remember, dealerships exist on more than sales along, service is their bread and butter.

 

And if all else fails, call a lawyer and have this taken care of. I know you may not want to but this is all about business, not personal. You made a purchase and should not have to either modify the product to make it work the way it was intended or not be able to trust it.

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