If you’ve followed the trials and tribulations of GM’s 8L90 eight-speed automatic transmission, then you know it has been a roller coaster of mostly bad. Over 60 technical service bulletins, warranty work, and multiple class action lawsuits haven’t stopped the ongoing problems. So for the 2024 Chevrolet Silverado and related vehicles, GM is switching over to the 8L80 eight-speed. 

Before this did GM try to fix the Silverado eight-speed transmission?

The Hydramatic 8L90, 8L80, and 8L45 eight-speed have registered thousands of complaints. These are for various issues like harsh engagement, sudden acceleration, stumbling upon acceleration or downshifts, premature parts wear, and even difficulty stopping. But the biggest complaints have come from it “shuddering” when in Drive. 

GM thought it had a fix in 2019 when it had affected vehicles undergo a trans fluid service. It replaced the recommended fluid with a lower-viscosity fluid. Unfortunately, that didn’t work. Service techs say the transmission’s torque converter “is uniquely untrustworthy,” according to Nextgendiesel. The latest version of the 8L90 began with the 2019 Silverado 1500.

How far back do these eight-speed transmission problems go?

And the problems aren’t recent. These issues go back to at least 2012. In fact, the 2012 and 2013 Chevrolet Silverado are two years to avoid, partially due to transmission problems. So, what has GM changed with this revised 8L90?

First, it is the 8L80 eight-speed, not the 8L90 10-speed automatic. It is already in the 2023 Colorado and GMC Canyon. Next, it will only be available with the turbocharged 2.7-liter four-cylinder engine, now called “TurboMax.” This, too, is already in the Colorado/Canyon. In fact, it is the only engine available for GM’s midsize trucks.

The other three Silverado engines available in 2024 using GM’s 10-speed automatic transmission. They include a naturally aspirated 5.3-liter V8 with 355 hp and 383 lb-ft of torque, the naturally aspirated 6.2-liter V8 with 420 hp and 460 lb-ft of torque, and the Duramax diesel with 305 hp and 495 lb-ft of torque.

What does GM say about the changes?

GM says it made internal changes between the previous eight-speed and the new 8L80. And it found that the gear ratios work better with the 2.7-liter engine than backing it with a 10-speed. Those ratios are First: 3.82, Second: 2.97, Third: 2.08, Fourth: 1.69, Fifth: 1.27, Sixth: 1.00. Seventh: 0.85, and Eigth: 0.65. GM says the extra torque of the 2.7-liter negated the need for two extra gears. 

In 2022, Colorado Chief Engineer Nick Katcherian told GM Authority, “I wouldn’t say it’s all-new, but from a component perspective, there’s a lot new in it. We learned a lot from the first-gen eight-speed on this truck. We’ve taken all those learnings and added more componentry, and really tried to move the eight-speed to a position where we could be proud of. We know what the customers have been complaining about in the current generation. We fixed everything that we could within reason.”

Not exactly shouting from the rooftops, but drive tests show it is improved, at least for certain issues.