Bought a 2021 Silverado With 8-Speed Transmission and Told The Salesman That Gear Shifting Isn't Smooth, After 30 Days I Took It To Dealership Again

The 8 speed is a nightmare. Almost all the trucks that come thru my shop are on their second or third trans or torque converter.
For anybody looking at that 8 speed market, do yourself a favor and get one with a bad transmission on the cheap. About half of them are chattering and slamming gears on the used market. Negotiate the deal and show the cost for a new trans. Get a new 8 speed trans. Have it tuned by a custom performance tuner to solve the torque converter issue. Keep it cool with the cooler mod. And you will have success. The problem with these 8 speeds is all due to GM keeping the truck fuel efficient as possible. The torque converter is constantly locking and unlocking. And slipping with each engagement. The new 10 speed transmissions stay locked and the issue is not present on the 10 speeds due to this. The 6 speeds will also benefit from taking it to a custom tuner and having the converter lock in only 5th and 6th gear.

Had this done with my 2019 Silverado LT about 2 years ago when it had around 35k. The dealer told me the early built trucks got a certain trans fluid and gm found it to be faulty, so mid production they switched to another trans fluid. So mine was all covered under the factory warranty and they did the flush and refill with the newer fluid. I'm at around 62k miles now and so far no issues.

When I worked at the dealer I’d just replace the transmission and save everyone the time and hassle.. the first one that came In for a shudder I went through the steps and later down the line it came back for rework... being flat rate I don’t get paid for rework so now I just order the transmission and replace it! Haven’t had one come back ever since.

This doesn’t work as stated. Yes you need to do all that but it’s also a line psi issue. Once tuned and raised all issues went away instantly. The fresh fluid / filter and what have you definitely didn’t change my 8 speed issues. Line psi did.

I had this issue on my Silverado truck. Just had the dealership service my transmission. They guaranteed it would fix the problem. I haven’t yet had any issues after the service.

Change your transmission thermostat, it'll make all the difference in the world. The factory stock setup makes the transmissions run way too hot!

He noticed the problem on the test drive before he bought the truck, he should have walk away. Wouldn't have had any of these issues.

I understand how he feels. I have been fighting with General motors on my express 2500 Van. Since it had 7600 miles on it, I have the 8L90 transmission, which has been a nightmare. The valve bodies have been replaced. The transmission control module has been replaced each of those twice.They even put a new transmission in or so they told me. After the new transmission drove it about ten thousand miles and the same hard downshifting started to come into play. I took mine to a Maryland dealership. Many times Koons Chevrolet in White Marsh. Finally, after they had done all the above mentioned work and put a new transmission in. They said there was nothing else they could do. But the vehicle is still at this writing under warranty, so they said, don't worry about it. My question to them and to GM was, what good is a warranty if you can't repair the vehicle.
Koons Chevrolet has even gone so far as to tell GM and myself that they will no longer service my vehicle with anything that has to do with the transmission. I was told that's as good as it's going to get Period! when you slow down, come to a stop, it shifts with a hard thud...it's as if somebody's bumping you from behind like it has from day 1. 2 Valve Body's 2 TCM's 4 reprogramming and a new transmission 8L90 and still having the same problem.

Never do a flush. Just a drain and replace.

Please stop with these garbage AI images. It makes the whole site look like a joke.

After 50 years of owning GM’s 40 years of driving Tahoes I WILL NEVER BUY ANOTHER !!!!!! This Bitch has run the company into the ground building NOTHING BUT JUNK !!!!

Using AI generated images on your posts, huh? If you keep doing that I'm going to block you. Just sayin'.

Something a lot of these reports don't tell you and I didn't know until recently is that you are to use a special transmission fluid that is mobile 1 blue label transmission fluid. This is the only transmission fluid that helps with this transmission.

Same issue at 115K miles.... Torque converter shutter. Goes away if you go to trailer tow mode and lock up torque converter...GM 8 speed uses carbon fiber on torque converter clutch which greatly improves durability and resistance to burning/glazing.Trans flush usually clears shutter issue. No need to drop pan, or replace filter.

This article is nothing but GM propaganda. As a Sierra owner since 2016 I can tell you for certain that flush doesn’t do anything. I’ve had 3, multiple fluid changes, multiple relearn (which by the way the good people at GM tried to convince me for more than 2 years that it is a smart trans just learning how I drive) and none of that crap did anything. They refused to replace the trans and it has devalued the resale of my truck. Just imagine a test drive with a prospective buyer when the transmission shifts so hard it feels like we’ve been hit by another vehicle.

My transmission went bad. I basically use it as a car without heavy loads. I was surprised to find out the reason is related to way the ecm let's the tranny slip when going from a v8 to a v4.
My mechanic had me buy a chip that shut that part of the ecm down.

GM 8 Speed 8L90 issues are not solved with fluid. Software. The issues are internal valve body components wearing out prematurely. T.C C valve. AFL valve and the Accumulator pistons. I run a transmission shop and have these trucks in regularly.

The correct transmission fluid for 8 speed transmission is Mobil 1 HP LV Blue label ATF. Not Dextron vi. Using Dex6 may be harmful and cause premature failure.

I too just purchased my 2021 Silverado, along with the extended warranty. Soon after I drove it off the lot the shuddering began. The day after I took it back to the dealer I stopped in to check with the service rep. He told me that GM had a service advisory telling them to drop the pan, do a double flush on the transmission, change the filter, and flush with Mobile ATF. Oh by the way, it is not covered by the extended warranty because it was a service issue. $890.00 later I dive it off the lot again and so far no issues with shuddering or shifting. Soon after, I read another service bulletin saying at the first sign of subject problem replace the TCM if it did not have a specific part number installed. I took the bulletin to my service rep and still three months later he has not answered my question as to why it was not checked or replaced.

I was having the same issue with my 2019 GMC Sierra 1500 SLT with 32000 miles dealership told me it needed a triple flush and would cost me $1039.00 they said this was a maintenance problem I told them this was a warranty issue so I carried to my mechanic for second opinion he changed the transmission fluid and filter for half the cost of the dealership and transmission seems to be working find dealership in the business to rip you off on high cost maintenance on issues that doesn't fall in timeframe 1000s miles of GM service guide line

I had transmission problems around 120k miles and I called a transmission company and he told me if Silverado have transmission problems they take it out and replace because if you change the fluid you will still have problems instead I had the fluid and filter change the problems stopped for a short period of time and came back after about 300 miles I had a transmission company changed my transmission and the problem stopped I will try the disconnecting the negative terminal on the battery for 30 minutes to reset the (TCM) if I have future problems I do like the truck but not the repair on the transmission (that I believe it was too soon ) or the repair on my rear differential at around 120K miles (that I believe it was too soon)

That's what Gm gets for switching to a foreign tranmission spring manufacturing company

You'll be back for a new transmission k. Another 40k miles..

We bought our Silverado 7 years ago, brand new. During the 1st 4 months we took our truck back 4 times for surging issues. After stopping for red lights/stop signs, pressing the gas pedal, our truck shifted forward or stopping for both it shifts forward. The dealer said there was no issue, it was the way we were driving. What? After having the transmission serviced, it still does the same thing. I have had the transmission serviced over and over, we now have 139,000 miles and still it shifts forward when stopping and starting. Has anyone else had this problem? Yes, many we have talked to, but, GM will not fix this. We heard that at 150,000 the transmission will have to be replaced!!! Our truck is a 2017 model.

Have a 2015 Z-71 bought new….regular services, at 98,000 miles another service, metal filings in the pan, had to replace with a rebuilt GM transmission $7,200 not counting the $500 wasted on a service for a bad transmission…GM knows that the 2015-2019 have had a problem, there should have been a recall on them. I found a site that has the information on a class action suite against GM…where that will go is anyone’s guess.PS also about 50,000 miles or so ago had to replace an AC condenser that GM knew was bas bad resulting in a broken weld….$1,000 later to replace, again another class action suit I joined and nothing has come of it to date….heck of a way to run a business….

Gm does not recommend using dexron fluid instead gm found out that mobile one fluid fixed the shutter condition the dexron would infact attract moisture and caused the problem so we at Hendrick chevy would flush the transmission 3 Times with mobile one and the problem went away I can't remember the tsb for that I'm now retired from chevy

Sealed transmissions, or at least transmissions that don't have a dipstick, have been plaguing people for decades. I have a 2007 Lexus GX470 with the so-called sealed transmission. It is very sensitive to fluid levels and age of fluid. I know because I DIY.