Chevy trans shudder issue - best fluid?

[ironman_gq]

The size difference from the 6L90e is 300mm vs 8L90e 258mm, which is 32mm total. No where near half the size. The biggest issue is the tuning, which is optimized for fuel economy. There are a lot of users on various messages boards that have done the tuning to the TCM to improve shifting that has also helped with the shuddering issue. The problem is the cost to do this, especially on the 17+ models with the newer TCM that has to be unlocked before it can be tuned. It can be upwards of $2000+ for tuning on the newer vehicles because GM has started locking down all the PCMs and TCMs. Not to mention it will void your warranty if you still happen to have one.

It's $199 ($299 if you need it programmed to your VIN) from HPtuners to unlock the TCM on the 8 and 10 speed transmissions, cost for actual tuning would depend on your tuner and what they charge for the service.

 

[Rat407]

Over on the GM-Trucks forum, the shudder thread is long. Some have luck with the fluid exchange to the updated fluid and some don't. What gets me is this issue has been around for a long time. GM was supposed to redesign the 8sp when the all new 2019 Silverado came out. Well, here we are in 2021 and some of the 8sp transmissions are still having issues.

GM isn't going 100% to the 10sp probably due to the weight and the fact that they have a ton of 8sps to use.

The 10sp in my Silverado is a dream. Love it and seems to keep the engine in it's peak torque when you need it.

I have seen posts where some have used AMSOIL's ATL in their 8sp and all is well, no issues.

 

[AngryScientist]

Update: Had the TSB performed this morning and picked the truck up. It's a night and day change for the better and not just eliminating the shudder but the overall shifting is much smoother. Time will tell if this proves to be a long term fix but for now, it appears the issue is under control. Fingers crossed.

 

[glock19]

Update: Had the TSB performed this morning and picked the truck up. It's a night and day change for the better and not just eliminating the shudder but the overall shifting is much smoother. Time will tell if this proves to be a long term fix but for now, it appears the issue is under control. Fingers crossed.

I hope it lasts for you. I had the TSB done on my 2017 Sierra and the shudder came back 2 days later. I ended up trading it in for a 10 speed F-150.

 

[buster]

Update: Had the TSB performed this morning and picked the truck up. It's a night and day change for the better and not just eliminating the shudder but the overall shifting is much smoother. Time will tell if this proves to be a long term fix but for now, it appears the issue is under control. Fingers crossed.

In most cases, not all, the fluid change works. My personal opinion is that there is a design flaw inherent in this unit, that can only be relatively mitigated by the new fluid.

The transmission was the biggest concern I had prior to buying the Colorado. I'm taking my chances with it. When it doesn't shudder, the transmission is great IMO. Shifts are quick and seamless. You can even go one step further and get the Trifecta tune which apparently does wonders for the performance.

 

[64bawagon]

Makes me wonder if there isnt some damage from the original fluid that is only masked when they use the correct fluid from the TSB. Its possible they would have avoided the whole thing entirely if they had just used the fluid on the TSB.
I think I would be nervous if I had a Duramax with the new 10spd Allison that isnt an Allison.

 

[Silver]

Can't wait for a 32 speed auto trans. I'm sure it will operate much better than these old school 8 speeds that spent a whole 2 seconds in each gear.