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GMC Forum: 2011 6 speed transmission for sierra
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  #1  
Old 09-29-2012, 08:28 AM
Rnelson Rnelson is offline
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Default 2011 6 speed transmission for sierra

This may be a tired and played topic but I am newly discovering that others have the same issue with their trucks. I understand the 6 speed transmission was modified to improve fuel efficiency. I have owned (and really liked) a number of GMC Sierra trucks but the thuds, clunks, delayed downshifts, and general stickiness of the transmission is a MAJOR letdown. It is as if the transmission was re-engineered in a vacuum while the accelerator and motor were never coordinated with the change. My primary questions is this: is there anything I can do about this? I can't sell the vehicle to anyone with experience driving full size trucks because it's an obvious flaw but I cannot keep driving this truck and accept the performance as is. Any insights would be greatly appreciated.
Thanks
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  #2  
Old 09-30-2012, 01:51 PM
GMC Customer Service GMC Customer Service is offline
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Quote:
Originally Posted by Rnelson View Post
This may be a tired and played topic but I am newly discovering that others have the same issue with their trucks. I understand the 6 speed transmission was modified to improve fuel efficiency. I have owned (and really liked) a number of GMC Sierra trucks but the thuds, clunks, delayed downshifts, and general stickiness of the transmission is a MAJOR letdown. It is as if the transmission was re-engineered in a vacuum while the accelerator and motor were never coordinated with the change. My primary questions is this: is there anything I can do about this? I can't sell the vehicle to anyone with experience driving full size trucks because it's an obvious flaw but I cannot keep driving this truck and accept the performance as is. Any insights would be greatly appreciated.
Thanks

Rnelson,
I understand your concerns and frustrations with this issue. Have you been in contact with GMC Customer Service in regards to your issues? I would like to look into this further for you. Can you please send me a PM with your VIN? I look forward to hearing back from you.
Thank you,
Stacy Chevrolet Customer Service
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  #3  
Old 10-01-2012, 11:16 PM
D.A.E.A D.A.E.A is offline
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Our dealer changed out our slip yoke with the nickel plated one. He checked the tranny firmware as there is a service bulletin out on 6 speed shift business, and they have repacked the slip yoke with grease. The only thing that has taken away the dreaded and 'normal' driveline clunk is driving in manual 5. It turns off the active fuel management. We get better mileage and most of all, almost zero driveline clunk. And doesn't shift all the time.

When it's time to trade this one in, we will not be getting another GM product with afm because of this. We are not impressed!
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  #4  
Old 10-02-2012, 09:15 AM
Z15 Z15 is offline
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Same here, I traded away a 2010 Sierra SLT E. Cab All Terrain because the AFM engine. Before I hit 10,000 miles they had to replace all the liflters because they rattled when cold weather got here. Not only that but they had to do it 2x, before it even left the shop they had to tear it apart again and replace 4 of the new lifers because they would not work. High priced junk, SM said they got parts from a shoddy source. I never had any trans issues but the constant engine vibrations at slow speeds got on my nerves big time. No fix for that, considered by GM engineers as a necessary evil to make the gov't happy.

Another issue that is showing up in recent years is oil consumption with AFM engines on the 2007, 08, 09, 10's because the shut down cylinders get so hot the oil cooks onto the rings and its starts to use oil. Usually its starts in the 30,000 mile range but depending on you drove it, it could sooner or much later. Those that baby them in order to get the best mileage seem to be the ones who have early oil consumption. If that is not bad enough, it will take GM a year or more before they will do much. They have about 3 temp fixes that try first then want to do oil consumption tests and many dealers just give the customers a very hard time during this process.
I like GMC's so I now have a 2012 Sierra Denali with the 6.2L engine and NO AFM. I will never buy an AFM engine or any hybrid junk vehicles.

Last edited by Z15; 10-02-2012 at 09:27 AM.
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  #5  
Old 10-02-2012, 01:58 PM
austinm austinm is offline
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Its also a problem on the v-6 equipped models with the 4speed auto as well. And because of it i'll never puchase a gm vehicle again. i like having a half ton but the throttle responce in this half ton is so lethargic sometimes i would be better off getting out and pushing.
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  #6  
Old 10-08-2012, 01:03 PM
loyaltogm loyaltogm is offline
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Default

I am in the same boat....owned gm's and chevy's my whole life.Never walked home EVER!!!Bought a 2012 Silverado....almost full load with 5.3 AFM and 6 speed auto. From the minute I drove away from the dealer I noticed all the symptoms you have including the engine almost falling on its face so to speak at the shift, while accelerating slowly. I returned and was told its different to drive and it has to learn my driving habits (usually takes a 1000 miles thet said) and that i need to be patient. Ok.... I drove it home from Winnipeg , Manitoba to thunder Bay, Ontario ..abouut 400miles. half way home i wanted to turn aroundf and bring it back it was running so shitty. Felt like the peddle was outta time with the engine kinda. Truck is fine...long asyou accelerate moderately. shifts good , sounds good feels good. Driving slow..as if in traffic pfff. What a pile.Anyway. i started to think that it felt kinda like bad fuel or water in the gas. long story short I put half a quart of methyl hydrate. ya I know it sounds like a lot but it was full of super unleaded. Anyway within 2 days and abot 30 miles it was completely different to drive. Shifted better, accelerated without the pause.almost feels like my 2000 Z7. Cant say that will help you but Ive had tons of mechanical experience and Im baffled by how much of a difference it makes. May have something to do with most car dealerships having a 1000 gallon tank of gasoline on the premisis to avoid going to the gas station all the time. Theyre above ground which from my experience working in the forestry industry, causes water for sure. Hot-cold, hot-cold cycles that happen daily cause massive amounts of condensation to form in the tank itself. This is avoided at most fuel providers because their tanks are buried underground where the temp remains constant. Might have something to do with it.My truck is night and day, and trust me it was almost going back permanently. i feel where youre coming from. its alotta cash to even remotely be dis-satisfied. cory
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  #7  
Old 10-09-2012, 04:02 AM
Z15 Z15 is offline
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Methyl hydrate is another name for methanol and you should NEVER use that in your GM vehicle. It will cause damage to the fuel system and you are crazy to use that stuff. Anywhere they tell to use it as a fuel additive they are selling you snake oil.

Quote:
Notice: This vehicle was not
designed for fuel that contains
methanol. Do not use fuel
containing methanol. It can
corrode metal parts in the fuel
system and also damage plastic
and rubber parts. That damage
would not be covered under the
vehicle warranty.
Quote:
Methyl Hydrate
Is there a difference between Methyl Hydrate, Methanol, and Wood Alcohol?
Answer: There is no difference between these products; it is just a different name for the same thing.

Methyl Hydrate is used for:
•Thinning shellac
•Cleaning brushes that have been used with shellac
•Cleaning windows, when mixed with water
•Defrosting air line hoses on tractor trailers & commercial vehicles during extreme cold temperatures
•Fondue fuel
•Fuel for marine unpressurized alcohol stoves
•Dissolving gums, resins, and celluloid
•Methyl Hydrate has a low freeze point and is suitable for de-icing applications, but it is not an anti-freeze for diesel fuel. It should not be added to diesel fuel, or used as a fuel.

Last edited by Z15; 10-09-2012 at 04:10 AM.
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  #8  
Old 10-11-2012, 07:53 PM
CEB66 CEB66 is offline
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Z15, Wasn't this your reply to my transmission complaints back in 5-21-2011 in the "2011 Sierra with 800 miles problem" thread?

Just drive it and don't worry. By the time you have 10,000 miles on the truck you won't notice it anymore as your driving habits will adapt to the trucks idiosyncrasies.

These electronic 6-sp transmissions along with Active Fuel Management (shutting down of 4 cylinders) have some quirks and I bet this is just one of them.
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  #9  
Old 10-13-2012, 05:22 AM
CEB66 CEB66 is offline
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Hi Rnelson,
In reference to GM Customer Service and helping "us" with our very ackward transmission; "Bull-Lowney!"
They won't look for a solution.
We've all been told "let me look into this for you" or let me start a "case" for you etc.
None have "found" a solution to this joke CAFE standard appeasement of a driveline powertrain set up.
Hopefully the 2013 Sierra Silverado guys don't get stuck with this clunk bang growl of a GM transmission you and I have.
At least we're far enough out that we don't have to put up with the insults of the sales managers and service managers when they told us "it has to adjust to your driving habits." They should be ashamed. Oh that's right, they're car salesman!

Last edited by CEB66; 10-13-2012 at 01:35 PM.
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  #10  
Old 10-25-2012, 05:17 PM
bob323@tds.net bob323@tds.net is offline
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Default Fed Up!

Folks, it seems that GMC doesn't give a crap about the problems we're having with this issue! I bought a 2012 Sierra SLE with the 6 speed/AFM/5.7L and noticed as I was driving off the lot the 'out of synch' AFM/transmisssion issue - the clangs/thunks/etc when down shifting or coming to a stop on an uphill incline, etc. Also the 'bogging down' of the engine when making a turn under light acceleration! I've reported the same problems EVERYTIME I've taken it into the dealership for routine maintenance and have asked them to check it out and fix it - only to be told everytime that there's nothing that can be done about it, that it's a characteristic of this combination of tranny, engine and AFM. That's why I say it's an 'out of synch' issue - each component seems to be unaware of the others while driving.

If GM is listening, can/will you PLEASE do something about this issue? We're all fed up with the problem and with GM's apparent lack of concern!
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