GM 8L45/90 Eight Speed RWD: Part 1 

The new ATF recently released seems to work fairly well but not always. Sometimes, computer programming and /or converter replacement may still need to be done. After 1500 miles though it should be okay.

My 2018 Colorado 4x4 developed the shudder in the first 7,000 miles. They did the fluid change and currently at 40,0000 shudder hasn't returned. Never have gotten a good explanation for the cause. Worried I should've bought the extended warranty.

I had the flush with the new fluid in 2019, 20k miles later and the shutter is back. They are swapping the converter now but I don’t see how it could have been bad for 20k shutter free miles.

@@cardplayer85 I'm worried about it coming back since I'm now out of warranty (2018 Colorado).....

Curious on the same thing, looks like this trifecta tune may have a slight nullification on the hard shift? Still looking for info though.

Bring it to chevy there is a special coverage on it and can be fixed for free under powertrain warranty. These clutch packs have a slow to fill issue and there are now updated pistons and calibrations to the tc to fix this issue

Due to vehicle complexity, today swapping transmission models is almost impossible. Aside from the 8L45 or 8L90 the only other possible option might be a six-speed like a 6L80. Even that would be hard to do.

@@TransmissionDigest thank you i understand. I have the 8L45 on my Atsv with new the mobile one synthetic transmission fluid. It’s working good since doing that fluid change, do you thinking this transmission will last a while or should i be worried about it?

Fluid change is a good start. The synthetic recommended one.

@@marty0715yt yup mine was shuddering as well...put the mobile 1 synthetic shifts and feels way better.

for awhile--

TCC shudder can be related to transmission fluid, computer strategy, torque converter or transmission issues. Engine-related issues can cause a similar feel. It does require a process of elimination to arrive at a fix.

Mine has all of the tcc issues plus it feels like driving over rumble strips at highway speeds. The dealership fixed mine. They told me to drive slower or live with it. I can't wait to trade that pizza sheet away. Already had the fluid change, lasted about 3k miles. Torque converter changed 4k miles later, no change.

My 2018 Sierra does the same exact thing. I’ve been complaining to my local dealership since I bought it new. It’s now over 60K miles and out of warranty. I’m beyond pissed at GMC.

Unfortunately, hard shifting and lock-up shutter is why a class-action lawsuit was filed against GM. New fluid seems to fix some of the lockup shutter issues but not hard shifting. Sometimes resetting shift adapts will work but not always. Shift quality is a cross between computer programming and solenoid/valve body function. Currently, to my knowledge, there is not an aftermarket fix. Sorry.

A hard 1-2 shift when it's cold is common with this trans due to clutch-fill times.

Sounds about right....these issues is the reason I got rid of my 2016 GMC. It sad really, as the GMC was great truck, just an awful transmission

@@1954saltydog Which is fascinating, because I've been driving a 2019 Silverado with the 8-speed and it's one of the best automatics I've owned. It's really a common situation with every new transmission. When the 4L60/4L60E was the new transmission, they were awful in the early years but later became great transmissions once the issues were solved. Then the 6L80E showed up and everybody absolutely hated it due to early issues. Once the issues were addressed, it because a pretty solid transmission. Then the 8L90 shows up and everyone hated it because of early issues, but once the issues with converter drainback and Dexron HP were fixed, it's becoming a good transmission. This isn't isolated to just GM either. The first few years of the ZF 8HP were notorious for issues. Even once it went into the Ram 1500, the first couple of years had plenty of complaints for hard shifts, bump downshifts, etc. Complaints came back again in 2019 when the new Ram 1500 received an "updated" ZF 8HP that caused all kinds of new issues with slamming downshifts, bump downshifts, becoming "stuck" in 2nd gear at a stop, etc. Ford had a lot of complaints with early 6R80's, the "updated" 6R80 in 2015, and the 10R80 when it was pushed into every new F-150 in 2018. When Toyota began putting the AB60E/F into the Tundra, it had issues with "slipping" sensations, solenoid failures, converter issues, etc. The 2016+ Tacoma's 6-speed has had massive complaints for flared shifts, terrible shift programming, delayed engagement, hesitation taking off from a stop, etc. The Toyota 8-speed that went into the Camry and other vehicles was infamous for torque converter failures, shuddering, delayed engagement, premature transmission failures, etc. It seems that no manufacturer has a flawless launch of a new or modified transmission design.

Run over to Toyota

Toyota has their fair share of transmission issues. Especially the 2016+ Tacoma, which has had nothing but complaints for flared shifts, delayed engagement, constantly shifting between gears (this is one of the worst issues), underfilled transmissions, seal leaks, hesitation issues, etc. That's on top of the 50% of owners that complain about howling rear diffs that Toyota claims is a wind resonance... even though the rear diffs howl when the truck is on a lift, stationary, and the rear wheels are turning.

Excellent decision.....there is a lawsuit against GM over this transmission.

Great I just Bought a ‘21 Zr2! 🤦 3500 miles on it so far!

A very expensive vibrator.

Yep, my '70 Chevelle has 197k on it and never had a trans issue! New fluid/filter every 30k is all. It's been towing boats all its life as well.