I have the misfortune of…
I have the misfortune of owning a 2019 Silverado LT 4wd with the infamous GM Hydra-Matic 8L90 8-speed transmission. I bought it "used" with only 82 miles on the odometer. The original owner returned it after 3 days because, according to the salesman, it was too much truck for him.
I had occasional rough shifts at first but learned how to drive so they didn't happen as often. I took it in and complained and was told "that's normal" and "that's a characteristic of those transmissions". It smoothed out some eventually and I lived with it.
I took the truck in for the recommended transmission service at 52K miles. I would have done it at 45K but I had a family emergency that required me to drive to Houston from Seattle and back. When I took it in, it was fine. I wasn't experiencing any problems with the transmission. When I picked it up afterwards, the service advisor told me it would probably shift rough for 500 miles or so until the computer relearned my driving style.
Things were bad right from the start. It shifted rough and short shifted between some gears. It would downshift and accelerate unexpectedly. It did this on wet pavement and caused it to fishtail. I almost lost control and nearly had a head-on collision. Later, as I was pulling away from a stop, the engine revved to 5,000 rpm but I wasn't speeding up. I thought the tires were spinning but it was the transmission slipping. It finally caught and it felt almost like I got hit from behind. Then the check engine light came on. The truck was dangerous to drive. I took it home and the next morning I took it to the dealership. They took it into the shop to check it out and later called me and told me it needs a new transmission.
I was charged $458 for the transmission service which destroyed my transmission. They charged me $495 for diagnostics fee to determine the transmission was junk. Then the biggie. They said it would be $12,000+ for a new transmission.
I questioned, rather loudly, how it could have failed when it was fine when I brought it in. The service advisor told me it was my own fault for going 7K miles over the recommended service interval. He then told me that the reason it failed was because the dirty fluid was holding everything together. But when they put in clean fluid everything fell apart. He actually said these things to me. Eventually, he said he would speak with the manager and see what they could do to help me out. When he called me back he said they had spoken to GM and GM had agreed to pay half of the cost of replacement. My half would be $6,291.39. That's on top of the $953 they charged me to destroy my transmission. I thought I had the warranty when I bought the truck because we had work done previously "under warranty". That magically disappeared when the trans failed.
Had I done my usual research that I normally would have before making a major purchase, I would not have bought this truck. However, I was offered such a good deal on this one that I knew it would be gone if I didn't buy it right away. Later, after reading about the trans issues, I figured I'd be replacing it at some point during my ownership. I can live with that. I still come out ahead. But I'll be getting rid of this truck asap and I'll never own another new GM product. I'll be buying my vehicles from a different source as well. They're called stealerships for good reason.