Much commented 8 speed transmission

BowtieSquatch · February 26, 2020

As I stated in a different 8spd posting, Other than the occasional Ka-Bang from Reverse to Drive, and the Hard shift from 1st to 2nd, its a good transmission. Responds well when needed and loves to tow.

Moend · February 26, 2020

14k miles on mine. No problem with the 8 speed. By far the most refined drive train I ever used on a pickup. And this might sounds boaring but I think it is plenty fast and responsive for a truck.

Glava2876 · February 26, 2020

4 hours ago, BowtieSquatch said:

As I stated in a different 8spd posting, Other than the occasional Ka-Bang from Reverse to Drive, and the Hard shift from 1st to 2nd, its a good transmission. Responds well when needed and loves to tow.

I just traded in my 2015 6.2 8A. Within 2k miles I had a bad 2-1 down shift clunk. They did a re flash and it was fine, but a few thousand miles later I had the "flutter" under slight acceleration> I took it in and they did the triple flush with the new fluid -from that point until 51k miles when I traded it in yesterday, it was great.

AD80 · February 27, 2020

Mine slams into reverse sometimes sounding like someone hitting my trans with a sledgehammer, shaking the whole truck, but while shifting Into drive and while driving it shifts smooth as silk. Build date 6/19.

Edited February 27, 2020 by AD80

Philipgonzales3 · June 15, 2020

On 2/23/2020 at 12:20 PM, Thomcat said:

...

All post 3/19 production, with the 3/19 door sticker or later build date, incorporate a factory fill of Mobil 1 Synthetic LV ATF HP transmission fluid instead of the previous DextronVI. As indicated in the tech article below seems Dextron VI is hydroscopic and operation with a hydrated solution of DextronVI would seem related the shudder problem. Otherwise why would GM spend tons of money equipping dealers with specialized equipment and instructions and drums of new Mobil1 stock for 100% replacement of all previous Dextron in the trannys and torque convertors? The Mobil1 is backward compatible and recommended for use in all 8 speeds instead of Dextron replacement. Just a thought but this could be related my first hard cold 1-2 shift if the accumulator bleeds down overnight might be the cause of the first 1-2 hard shift.....as far as I'm concerned a quirk not a defect.

Sweet, my truck has a build date sticker of 3/19. So that means I have the good juice right?

winks79 · June 15, 2020

Mine has a build date of 12/18. Had the shutter and the slamming in gear going from reverse to drive, which was really delayed. Did not start having issues with it until about 5k miles or so. Dealer flushed and refilled it and after about 500-1k miles it just stopped and has been doing great. Had the 8 speed in my 18' Sierra and never had these issues. Mine was not really that bad, but I did notice it. I really like the 8 speed, and will buy one with a 10 speed next, since it looks like you can't get the 8 speed any longer. At least all the 20' models I have seen have the 10 speed now.

Cpl_Punishment · June 16, 2020

4 hours ago, winks79 said:

Mine has a build date of 12/18. Had the shutter and the slamming in gear going from reverse to drive, which was really delayed. Did not start having issues with it until about 5k miles or so. Dealer flushed and refilled it and after about 500-1k miles it just stopped and has been doing great. Had the 8 speed in my 18' Sierra and never had these issues. Mine was not really that bad, but I did notice it. I really like the 8 speed, and will buy one with a 10 speed next, since it looks like you can't get the 8 speed any longer. At least all the 20' models I have seen have the 10 speed now.

The 2020 4x4 Sierras all get the 10 speed but some of the Silverados still get the 8 speed

Trza · June 16, 2020

My previous 2015 All Terrain had a bad 1-2 shift every now and then. I now have a 19 Elevation with a 06/19 build date and the 8 speed has been extremely smooth.

I test drove a baby Duramax 10 speed Denali before buying the 19 Elevation and really didn't notice much a difference in the shifts....however, the low end torque and pull from a red light on the 3.0 is a different animal altogether!