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Chevy Silverado and GMC Sierra Transmission Problems



  • "The torque converter spends as much time as possible "locked" when it's in gear. That's what you are feeling. The brakes work when applied. "

    I never would have guessed that brakes work when applied. And yes, I understand that the converter is programmed to lock up as much as possible. HOWEVER, the converter should NOT be locked at low speeds, like below 25MPH, and it should NEVER be locked when I am trying to stop and am at a slow speed. Even with the brakes applied, I can feel the transmission still trying to push the vehicle forward, and it fights the brakes. If the stupid thing would just uncouple and coast, problem solved. The tranny waits until the last possible second to downshift, forcing the RPM's up to keep the truck from stalling, and as the slush box finally drops to first, the ECM can leave the throttle alone. I have seen the tach drop to 300 or 400 RPM's when coasting to a stop, and due to the fly by wire throttle, the computer determines that it needs a bit of throttle to keep from stalling. This is what I am talking about. Solenoids are sticking in this transmission, or are very poorly designed.
  • ceb66 is 100% right on the driveability issues with the late model GM trucks. Aside from the shifting problems I already mentioned, at around 40-45mph and a steady cruise, I can watch the tach, and it's like the tranny slips or almost starts to come out of lockup. The tach needle spikes up about 100-200rpm at least once every few seconds. I can feel and hear it driving, too. I haven't really noticed any issues with the AFM, unless this is it. I just know that every GM truck I have had since my 2005 Sierra Denali 4 speed has shifted far worse than the 2005 and prior gas trucks I have had (the exception being the two Duramax's I had, which were 2006 and 2011 models, which had awesome Allison tranny's). Ever since around 2007, they went to the fly by wire throttle, and I just don't think the ECM and TCM do a good job of working together. I can't believe that GM all of a sudden can't make a tranny that works properly. I want to believe it is a software issue, whether intentional or not. All I ask is they FIX IT.
  • transmission or transfer case started acting up today - 3 times while driving on highway the engine revs up, speed drops and there is a loud grinding sound from the transmission area - sounds like shifting a manual transmission without the clutch and not getting the gears engaged - stopped the first time and made sure the transfer case manual shifter was in 2 wheel high and it was - the next two times let off the throttle and noise stopped and normal operation returned - not fun when cruise control is on - fluid levels are good - no trany problems before this - occurs when vehicle goes over small bumps on interstate highway - will check the fluid in the transfer case for metal filings and check the shift linkage but not sure where to go from there - any ideas?
  • obyoneobyone Posts: 8,065
    To arrive at the EPA mileage GM programs their trans. The dealer can override the shift points (so can some of the performance programmers) to solve your driveability issues. The problem with the dealers programming is that once their tech 2 is disconnected you will lose the shift points. That leaves you with an aftermarket programmer which runs between $300 and $500. Whether it's worth the money or not is your call. GM will not approve a reprogram as it will alter the mpg which is posted on their trucks nationwide. And yes I agree with you it sucks.
  • ceb66ceb66 Posts: 70
    edited November 2012
    Hi bigman,

    Don't get distracted while driving, however, switch your driver display to "Instant Economy". Watch and feel it in the mid 40's! The annoying lag and growl will coincide with the 5.3 liter 6 speed awkardly trying to figure out "should I be in 6th at 45 mph, or 5th or maybe 4th. 4 cylinders? Maybe 8? Wait a minute, I'll just pick up the slop and BANG"!

    The Feds upped the CAFE standards right after the $54 Billion "bailout" (TARP).

    Hmmm? General Motors tweaked these things to squeeze out mileage. They appeased the Feds and still haven't paid back the "loan"(to tax payers).

    GM kissed.... and politely went along with the CAFE increase (which the car manufuacturers rarely if ever do) and we got stuck with a very confused computer-controlled powertrain/drivetrain combo.

    Be prepared. They're pushing for higher CAFE standards in 2017 (I believe in the 40 MPG range!). That means more hoaky tricks to appease. I've had many GMs. This may be it.

    Hopefully nobody else gets stuck with one of these things like I and others have.

    Thanks GM. You should be proud. You've made the Federal Government happy.
  • chuck1chuck1 Posts: 1,405
    I've had many GMs. This may be it.

    Yes, please unload it and move on.
  • ceb66ceb66 Posts: 70
    edited November 2012
    Potential General Motors truck buyers, make sure you test drive this 5.3 liter 6 speed Active Fuel Management AFM General Motors truck extensively at 45 MPH before purchase.

    Ensure it doesn't clunk lag growl and sometimes bang .

    If it does, don't let any GM employee insult you by saying it has to adjust to your driving habits!
  • Ceb66...

    Really?! I'd call the dealerships GM and let him know what kind of people he's hiring...idiots.
  • obyoneobyone Posts: 8,065
    I think ceb66 was referring to chucky.
  • ceb66ceb66 Posts: 70
    edited November 2012
    Hi lady3bglover,

    There must be alot of "idiots" working as sales managers for GM! I'm exagerating. I really don't think so. They're just doing what the corporate people tell them to do. Contrary to the sales numbers, they're under a huge amount of pressure do to GM's financial situation.

    However; many, many new 2010, 2011 and (apparently) 2012 GM Sierra and Silverado buyers have been told exactly that when they complain of the wierd/ackward transmission; "it has to adjust to your driving habits"!

    Insulting to anyone with even a minimal mechanical background. I walked out when I was told that.

    If they're using lines like that and there is an internal bulletin addressing the tranny/AFM issues, it's definitely widespread and they're keeping it under wraps. I know that from talking to techs and GM employees. My family worked in the industry.

    After GM took the TARP money, they seem to have gone back to their old (1970s/1960s) approach to the customer; "just get the car sold, and use whatever line you have to to get them out of here if they have a problem."
  • Ceb, I tend to agree with you that most of the weird behavior in the drivetrain is software related, and it is probably related to the CAFE standards. My question to GM is if this is actually what is happening, how much improvement can it honestly make? Like 1 MPG? What tricks to you have up your sleeve for when you need to squeeze out another 5 MPG? I can't wait for this to happen. If I could easily reprogram my engine/tranny to behave like my 2005 Sierra Denali, I'd do it in a minute.
  • chuck1chuck1 Posts: 1,405
    edited November 2012
    No one ever denied that the 6 speed transmission and/or AFM sometimes does not make for a smooth power train.

    However, with the number of SOLD units with the six speed transmission on the road-a software program reflash to fix or improve the power train is not going to happen IMHO, it's simply too costly.

    And it doesn't matter how many negative posts people put on this board.

    You can either live with it or buy a Toyota.

    So far it HAS NOT AFFECTED RELIABILITY of the vehicle. They sell 40,000 units a month and I have yet to sell one sitting over on the shoulder of the highway.

    Also, you can buy these trucks for $10,000.00 off sticker and save thousands over comparable trucks.
  • chuck1chuck1 Posts: 1,405
    You could reprogram with an aftermarket tune. There are several on the market that have had good reports. However, if you have a 100K powertrain warranty IT MAY void it.

    COST between $300-$500.00
  • Yea-I will go pullout those TPMS sensors now.
  • ceb66ceb66 Posts: 70
    If you're a new potential 2012 2013 GM truck buyer make sure you test drive these trucks extensively.

    The 2011's CLUNK LAG GROWL and sometimes BANG as the Active Fuel Management kicks into 8 cylinders.

    Ask the salesman if you can constantly feel the AFM working.

    Make alot of slow right turns.

    Most of all test drive it at 45 MPH on level ground.
  • chuck1chuck1 Posts: 1,405
    edited November 2012
    Those browsing this board will see your posts for what they are. A personal vendetta. The owners of the 39,000 trucks that ae purchased each and every month don't post how satisfied they are.

    The vast majority of the 1300 plus posts are from 14 people.

    On our way to 1500!!
  • ceb66ceb66 Posts: 70
    If you're a new potential 2012 2013 GM truck buyer make sure you test drive these trucks extensively at 45 MPH.
  • chuck1chuck1 Posts: 1,405
    edited November 2012
    Congratulations to Chevrolet/GMC Trucks for October sales gains over a year ago!

    Total YTD units are 463,688

    Total SIlverado/GMC sales for October are 53,307.

    This represents Chevrolet Silverado sales up 5.7% from a year ago, along with GMC truck sales up 9% in from the same period.

    They are a great value right now!
  • ceb66ceb66 Posts: 70
    If you're a new potential 2012 2013 GM truck buyer make sure you test drive these trucks extensively at 45 MPH.
  • chuck1chuck1 Posts: 1,405

    It looks like they are test driving them. AND BUYING THEM!
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