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John Goreham Contributing Writer, GM-Trucks.com 4-25-2019 Back in December, GM-Trucks.com member Jammin87SS posted a note here about a class-action suit related to GM 8-speed automatic transmissions. This transmission was used widely by GM, including in the Sierra, Silverado, Colorado, and Canyon pickup trucks. Owners have been complaining of shuddering and hesitation. Owner of a Silverado, Ed T., wrote a typical description for CarComplaints. He says, "Ever since I bought this truck new there has always been a shifting problem. This problem occurs whenever I slow down to a fairly low speed and then accelerate. When I accelerate there is a hesitation for a second or 2. This is very annoying and could potentially be dangerous. I have contacted my dealer and he just says "that's the way they shift, no fix"??? Dealer also stated that the transmissions have a learning chip and shifts the way a person normally drives - that's total BS. I have had my truck for over 2 years and it still shifts poorly. Besides the above I love my truck very much, GM just has to fix this problem..." GM knows there is a problem. It has issued both notices to its dealer's technicians and also TSBs. However, it has yet to find a solution that works. There is a class action suit that you can learn more about here. Our questions for our members are; 1) Have you experienced any issues with your 8-speed, and 2) was the dealer able to fix it? Let us know in the comments below.
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Hi everyone, I just purchased a 2016 GMC Sierra SLT Crew Cab All Terrain X a few weekends ago. The AFM (Active Fuel Management) is such a pain when switching from V4 to V8 mode at low speeds (non-highway driving) because I hate the "bogging" or "hesitating" feeling the truck gives off and the exhaust tone is UGH... I had a 2007 Avalanche and used a Range Technology device to disable it. But overtime I would have to pull the device out and plug it back in because it wouldn't activate sometimes. Been reading on this forum about the Range device for the newer Sierra's and people have been having issues with them and could mess with the computer overtime. So I won't be going that route. Another option is to get a tune like BlackBear and get it disabled or set a minimum speed of when the AFM activates. But a tune isn't an option for me right now because I want to keep my warranty as long as I can. Someday BlackBear tune will in my future! So I decided to try something. For the last couple days I have been driving in Manual mode "M" and setting it to M7 (7th gear) and driving like normal (non-highway driving). I was shifting gears up ( + ) and down ( - ) because I thought that was what you were suppose to do but I found out I can just set it to M7 and not worry about shifting, it does it for me, it just doesn't go into M8 (8th gear), which I don't need when I am going less then 50mph most days. I watched it stay in V8 mode stay the WHOLE TIME! The only time it went into V4 mode was when I shifted into M8 and then I switched back to M7 and it went back into V8 mode. So I think I found a workaround without having to void my warranty with a tune or messing up my computer with a AFM disabler device. I want to get your thoughts guys, will running in Manual "M" mode ruin the transmission in anyway? Not using M8 (8th gear) for slow speeds have long term affects with that gear? I am going to do this for another week or two and report my findings. This guy is happy when my truck isn't "bogging" or "hesitating" and have full power!!!
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Here's my new to me CPO 2016 Chevrolet Silverado 1500 5.3/8spd LTZ w/ LTZ Plus Package and Z71 Package. Silver Ice on Jet Black Here are pics the day I picked it up from Lone Star Chevrolet in Houston TX on Feb 28. Mods are going to be the usual and will be listed below Thanks for looking!
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Late last night, a GM-Trucks.com member noticed that the 2015 Silverado fuel economy numbers had been updated at fueleconomy.gov. Only available with the 420-horsepower 6.2L V8 engine, GM's new 8-speed will net Silverado and Sierra owners 1-additional MPG in both city and highway driving. We will report on the "official" numbers if and when the company releases them publicly. Compared side by side to the 2014 6-speed View attachment: 2015MPG.jpg(Thanks to gone_fishing for this graphic) -
By Zane Merva Executive Editor, GM-Trucks.com 10/13/2014 Despite no official announcement or press release, the official fuel economy figures for GM's new 6.2L & 8-speed transmission seem to finally be out in the open. Late last night, a GM-Trucks.com member noticed that the 2015 Silverado fuel economy numbers had been updated at fueleconomy.gov. Only available with the 420-horsepower 6.2L V8 engine, GM's new 8-speed will net Silverado and Sierra owners 1-additional MPG in both city and highway driving. We will report on the "official" numbers if and when the company releases them publicly. Compared side by side to the 2014 6-speed (Thanks to gone_fishing for this graphic)
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As many truck and SUV owners know, the performance of the transmission is a big part in how confident you feel behind the wheel. While only a single part in a complex powertrain, the transmission is the glue that links an engine to the road. When the transmission hesitates, the entire vehicle’s performance suffers. A great vehicle needs an equally great transmission. After only a few minutes behind the wheel it became obvious that shifts are quicker and smoother than the past generation 6-speed. Having two more gears allows the engine to stay in the sweet spot of the RPM range more often. Tip into the throttle and with no drama the 8L90 quickly snaps to the right gear. However, the most noticeable change is how well shifts are managed by the faster next generation transmission controller. Dependable and crisp transmission performance is a benefit in any situation. A slight bump in fuel economy is the icing on the cake, allowing for a +1mpg bump in fuel economy. Under full throttle we found gear changes effortless, quick, and solid. Under light throttle we could barely notice the vehicle had shifted at all. Where the past generation 6-speed sometimes gets confused or doesn't shift as cleanly as we’d like, the new 8-speed was always seemed on point. Unfortunately, we're slightly surprised to see that manual shifting with the 8-speed hasn't changed. Commands to select a specific gear using the shifter stalk are still only a suggestion, with the transmission controller having a final say. In our short test, shift requests sometimes took seconds if the truck didn't agree with the gear we requested. We drove an 8L90 equipped 2015 Sierra Denali and Yukon Denali on urban streets during rush hour. We did not get an opportunity to measure fuel economy. While only available with the 420-horsepower 6.2L EcoTec V8 during model-year 2015, expect this 8-speed to be available in the rest of the full-size truck and SUV line in the near future. When we have an extended amount of time with another 8-speed truck we will report back with fuel economy figures and more driving impressions. -
By Zane Merva & Josh Merva GM-Trucks.com 10/29/2014 Last night we had our first opportunity to drive a 2015 GMC Sierra Denali and Yukon Denali equipped with GM’s new Hydra-Matic 8L90 8-speed automatic. In August we drove a 2015 Chevrolet Corvette with the 8-speed but this was our first chance to try the transmission in a K2XX application. As many truck and SUV owners know, the performance of the transmission is a big part in how confident you feel behind the wheel. While only a single part in a complex powertrain, the transmission is the glue that links an engine to the road. When the transmission hesitates, the entire vehicle’s performance suffers. A great vehicle needs an equally great transmission. After only a few minutes behind the wheel it became obvious that shifts are quicker and smoother than the past generation 6-speed. Having two more gears allows the engine to stay in the sweet spot of the RPM range more often. Tip into the throttle and with no drama the 8L90 quickly snaps to the right gear. However, the most noticeable change is how well shifts are managed by the faster next generation transmission controller. Dependable and crisp transmission performance is a benefit in any situation. A slight bump in fuel economy is the icing on the cake, allowing for a +1mpg bump in fuel economy. Under full throttle we found gear changes effortless, quick, and solid. Under light throttle we could barely notice the vehicle had shifted at all. Where the past generation 6-speed sometimes gets confused or doesn't shift as cleanly as we’d like, the new 8-speed was always seemed on point. Unfortunately, we're slightly surprised to see that manual shifting with the 8-speed hasn't changed. Commands to select a specific gear using the shifter stalk are still only a suggestion, with the transmission controller having a final say. In our short test, shift requests sometimes took seconds if the truck didn't agree with the gear we requested. We drove an 8L90 equipped 2015 Sierra Denali and Yukon Denali on urban streets during rush hour. We did not get an opportunity to measure fuel economy. While only available with the 420-horsepower 6.2L EcoTec V8 during model-year 2015, expect this 8-speed to be available in the rest of the full-size truck and SUV line in the near future. When we have an extended amount of time with another 8-speed truck we will report back with fuel economy figures and more driving impressions.
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----------------------- 2015 Chevrolet and GMC Pickups, SUVs to Offer Eight-Speed Transmission DETROIT – Chevrolet and GMC have confirmed a new eight-speed automatic transmission will be standard on 2015 Chevrolet Silverado, GMC Sierra and GMC Yukon Denali/Yukon XL Denali models equipped with the 6.2L EcoTec3 V-8. The GM-developed Hydra-Matic 8L90 eight-speed is approximately the same size and weight as the Hydra-Matic 6L80 six-speed automatic. Its 7.0 overall gear ratio spread is wider than GM’s six-speed automatic transmissions, providing a numerically higher first gear ratio to help drivers start off more confidently with a heavy load or when trailering. The 8L90 also enables numerically lower rear axle ratios, which reduce engine rpm on the highway. With 420 horsepower and 460 lb.-ft. of torque, the 6.2L EcoTec3 V-8 is the most powerful engine offered in any light-duty pickup, and offers a maximum available trailer rating of 12,000 pounds, based on SAE J2807 Recommended Practices. As with other EcoTec3 engines, it seamlessly switches to four-cylinder operation under lighter loads to improve fuel economy. Additional technical details and the EPA estimated fuel economy will be announced closer to the start of production in the fourth quarter of 2014. -
Zane drives the 8-speed - read his thoughts - Correct Link By Zane Merva Executive Editor, GM-Trucks.com 7/18/2014 General Motors has confirmed that every 2015 full-size truck and suv equipped with the 6.2L EcoTec3 engine will be offered with a brand new GM developed 8-speed transmission. This includes the Chevrolet Silverado, Suburban, Tahoe and GMC Sierra, Yukon, and YukonXL. The new Hydra-Matic 8L90 eight-speed is similar in size to the outgoing 6-speed and will allow lower rear axle ratios for improved fuel economy. Fuel economy and additional specifications for 8-speed equipped vehicles will be announced later this year. ----------------------- 2015 Chevrolet and GMC Pickups, SUVs to Offer Eight-Speed Transmission DETROIT – Chevrolet and GMC have confirmed a new eight-speed automatic transmission will be standard on 2015 Chevrolet Silverado, GMC Sierra and GMC Yukon Denali/Yukon XL Denali models equipped with the 6.2L EcoTec3 V-8. The GM-developed Hydra-Matic 8L90 eight-speed is approximately the same size and weight as the Hydra-Matic 6L80 six-speed automatic. Its 7.0 overall gear ratio spread is wider than GM’s six-speed automatic transmissions, providing a numerically higher first gear ratio to help drivers start off more confidently with a heavy load or when trailering. The 8L90 also enables numerically lower rear axle ratios, which reduce engine rpm on the highway. With 420 horsepower and 460 lb.-ft. of torque, the 6.2L EcoTec3 V-8 is the most powerful engine offered in any light-duty pickup, and offers a maximum available trailer rating of 12,000 pounds, based on SAE J2807 Recommended Practices. As with other EcoTec3 engines, it seamlessly switches to four-cylinder operation under lighter loads to improve fuel economy. Additional technical details and the EPA estimated fuel economy will be announced closer to the start of production in the fourth quarter of 2014. Attached Images: Click here to view the article
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I had my first chance to try out the new Hydra-Matic 8L90 yesterday at GM's Milford Proving Grounds. Although it was in a Corvette Stingray, I feel that I can give you all a preview of what the new 8-speed might add to the Silverado, Sierra, and other K2 platform models. If you want to hear about the 8L90 in the Stingray, head over to autoinsane.com and read my article: 8 new reasons to love the Corvette Stingray. On the pickup side, the new 8L90 will add a considerable amount of polish and refinement. It's an all new design with second generation control systems. It also fits in the same space and (at least in the Corvette application) weighs 8lbs less. The housing and input/output shafts will be different in the pickup application but the internals will be the same. Programming, shift algorithms and other fine tuning will vary by model and make. I drove the 8-speed on GM's Milford Road Course at speeds over 100mph and with no restrictions. Summed up, it's the next best thing to a Porsche dual-clutch PDK. I was very impressed and have high hopes for its performance in the K2 platform. I can see the quicker and firmer shift abilities of this transmission helping towing/hauling confidence. The wider ratio of gears will mean even quicker acceleration and better fuel economy. I think the most noticeable feature, however, is that you'll notice the transmission less. Partial throttle shifts are butter smooth and never hesitate. Some quick notes: No shift slop, as we've sometimes experienced with the current 6-speed Very well tuned rev-matching on downshift A wider range of shift feel than the 6-speed. Ranges from very smooth to harsh, depending on throttle Built to handle up to 650 lb-ft of torque. Seems very mod-resistant. Quicker CPU/processor and a handful of new sensors to measure almost every rotating shaft at any given time 6.23msec between sensor measurements/adjustments Added 1mpg to Corvette highway fuel economy Want to see and hear how it shifts? Watch this video of me riding with a GM engineer. I hope this is useful to someone.
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See this thread for updates: http://www.gm-trucks.com/forums/topic/162938-2015-silverado-sierra-to-get-8-speed-transmission/
