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GM 8L90 8 Speed Transmission Experiences

3K views 8 replies 7 participants last post by  540 Olds 
#1 ·
I've been thinking of buying a new 2WD Sierra with 8 speed transmission. I've been reading GM has ongoing problems with harsh shift and shuddering issues with more than a few unhappy customers and even a class action lawsuit against GM. Just wondering if any of you have a 2019 or 2020 pickup with this trans and your experience so far. I don't really need a 4WD, but it comes with a 10 speed that seems to have a better reputation. I don't want to purchase a known dud, but hoping GM has this 8 speed ironed out.
 
#4 ·
i might have seen 2 apart since they came out.Id say that a low percent problem.Our vehicles have very little transmission problems anymore compared to the 4l60 of 10 years ago.Scatter torque converter shudder but very minimal problems.
 
#6 ·
I've been thinking of buying a new 2WD Sierra with 8 speed transmission. I've been reading GM has ongoing problems with harsh shift and shuddering issues with more than a few unhappy customers and even a class action lawsuit against GM. Just wondering if any of you have a 2019 or 2020 pickup with this trans and your experience so far. I don't really need a 4WD, but it comes with a 10 speed that seems to have a better reputation. I don't want to purchase a known dud, but hoping GM has this 8 speed ironed out.
My son-in-law recently traded his $58,000.00 2016 1500 4WD 6.2 8L90 on a 2019 Jeep because GM/Chevrolet failed to address/repair that very problem and just paid him lip service. Other than that problem, it was a very nice truck with all the creature comforts and was much quieter going down the road than my wife's Honda Accord!
 
#7 · (Edited)
I did some reading on the 8L90, and GM was struggling to come up with a fix. I think they determined water absorption into the fluid was at least one of the issues and changed to Mobil One blue label fluid. There were also problems with the converter along with software bugs in upshift/downshift timing events. That's the reason I asked specifically about 2019/2020 models to see if they had a good fix in place.
BTW, the 6 speed in my 2011 Sierra sometimes gets 'confused' if I accelerate really hard and quickly back out of the throttle. It wants to stay in a lower gear at a higher rpm than needed after I let up on it. Other than that, it's been golden.
 
#9 ·
I don't have a "dog in this fight", but after reading the above link...When you tell me there is only ONE fluid that will work in a mechanical unit/part ..I have to throw the "BS" flag on what's REALLY going on..

On another note, my son had a Chevy Colorado with the 5-banger Isuzu engine; infamously known for valve seat/burnt valve problems. We didn't know it when he bought the truck, and problem didn't surface til 50-120K mile mark. After MUCH complaining form numerous customers GM did extend warranty(100K or 7 years) to all Colorado/Canyon owners, but still didn't change the fact they had a defective engine in millions of vehicles..

From an engineering standpoint, how many gears are enough?? Increased mechanical complexity...where is the point of diminishing returns.??

Good luck with your decision; it's never fun to end up with a constant, long term problem..
 
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