Interesting Read on 8L45/8L90 Transmission and the issues that plague them...

0REDSOX7 · September 2, 2020

I found this article posted in one of my FB forums for the Silverado and found it to be rather interesting. I tried searching to see if it was posted before, but I didn't find it (my search skills are not that great), but, thought it explained the issues (and how to fix them) rather well...

https://gearsmagazine.com/magazine/what-is-causing-that-a-look-at-the-gm-8l90s-most-common-concerns/?fbclid=IwAR1PP-PrKZdPE0u4CMPgAneomRh9UzeUgBIivggvfYrWFisq0E7hssJe2tE

Vigilante375 · September 3, 2020

So it seems that it may be better for us that have the shudder problem to have the fluid completely flushed and the new, updated fluid, put in then drive for 400 or so miles and see if it goes away. But like the author said, that might not be the fix for everyone.

Thanks for sharing.

Edited September 3, 2020 by Vigilante375

HapaTrailBoss · September 4, 2020

That shudder happened infrequently after the flush, but often enough that it made me question the longevity of the transmission. I moved on and got a 20 TB with the 6.2 and 10 speed. Cross my fingers it's been great so far.

econometrics · September 5, 2020

Very good read, thank you OP.

I’ve decided to just live with my 8spd and all its intermittent issues. They are not as frequent as when I first had the new truck. After 12K miles, it’s still not a “smooth” transmission, but I’m not going to waste time with my local dealer trying to remedy this. They’ve proven to me over and over that they cannot fix issues like this, even with TSBs out on them.

I’m just going to enjoy the truck and upgrade to a 2022 or so with a 10spd.

SLTSIERRA · December 9, 2020

I have a 2018 GMC Sierra SLT 4x4 with 6.2 and the 8 speed 8L90 transmission. I had the transmission flushed by the dealer at 18,000 miles when the torque converter began to shudder at steady speeds between 45 and 60 miles per hour. It functioned fine for the next 1500 miles or so. However, now at 20,000 miles its not shifting smoothly and yesterday with the transmission cold, I shifted from reverse to drive and the transmission hesitated when I pushed the accelerator. It felt like I was in neutral, the rpms revved before the truck moved. I'm not happy that GM continued to produce a transmission that they knew was defective. I've been a GM man since I was old enough to drive,,,I'm now past 60 and I tell ya, I would not buy a GM product with the 8L90 transmission. If I replace this truck I will research other makes....I'm no longer a proud GM owner.