Chevy trans shudder issue - best fluid?

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AngryScientist

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18 Chevy Colorado V6/8-sp trans. 29000 miles.

Just developed the dreaded, well known shudder issue on light acceleration. There is a TSB out there to flush the trans with new Mobil 1 Synthetic LV ATF HP fluid; which allegedly corrects the issue in the torque converter clutch area if the wear is not too bad/caught early, it's a new torque converter if not.

Has anyone got any insight on why the older dex VI fluid caused problems that the Mobil product abover remedies or if maybe there is something even better to run in this trans to prevent shudder in the future?

This work is being done under warranty, so I'm just going to let them do it, but in the future i plan to drain refill every 30k or so and want the best fluid possible.
 
I believe the current fluid is Mobil 1 Synthetic LV ATF HP with the blue label, so if you're going to do drain and fills every 30k make sure you get the kind with the blue label not the older version with the black label.
 
We had a similar issue at Acura on the V6 models. Fluid gets overheated and breaks down causing the shudder. Guess the Mobil 1 fluid will last much longer at higher temps than the original fluid.
 
GM has contracts with Mobil 1 which is likely why they're recommending Mobil's fluid over other brands of the same spec.
 
AngryScientist said:
There is a TSB out there to flush the trans with new Mobil 1 Synthetic LV ATF HP fluid; which allegedly corrects the issue in the torque converter clutch area if the wear is not too bad/caught early, it's a new torque converter if not.
Click to expand...

Are you sure the prior fluid was Dexron VI or the original OEM LV HP? There was some prior discussion (but I never saw any of it confirmed by documentation) that the OEM LV HP formulation was hygroscopic, that is, it attracted moisture. Supposedly Mobil was tasked to modify and to improve the formulation.

My theory (and it's just a theory for now until more data appears) is that the moisture modified (if that were the case) the dynamic friction coefficient of the previous fluid to the point where it was no longer effective. I also suspect the TCC's pressure programming and timing were much different from prior transmissions' programming.

Perhaps one of our AT experts has additional information.
 
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^ +1 ...I have a 17 Silverado that had this issue and flush fixed . Unlike older gm trans torque converter clutches that would lock up after initial acceleration the newer GM TCC is almost constantly slipping. Moderate change in the fluid and the TCC slipping gets choppy as the system struggles to smoothly control it.
 
AngryScientist said:
Just developed the dreaded, well known shudder issue on light acceleration.
Click to expand...
I literally just talked to my neighbor with the same truck and trans with 18,000 miles and he has the exact same problem. GM told him the trans has the wrong trans fluid.
 
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i hope my 10spd wont be such a trashcan but it's new age gm so we'll see.

Only got a 2021 just because i still own the venerable 05 with 314k on its original internals engine, trans, front and rear diff, and t case all without issue and what i would honestly say is piss maintenance on top of that. Heck even all of my shock absorbers and ac are untouched these old gm's were so good.
 
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Yea, all of these "innovations" are in the name of pushing greater fuel efficiency, but it's not working; at least for my V6 Colly. I get terrible gas mileage and the 8-sp regularly hunts for the right gear on the highway at 75-80mph in hilly terrain. The direct injected engine is very nice though and makes great power. i do hope the trans flush is a good long term fix, as i do like the truck and tend to keep vehicles to 300k or so also, just not sure if this modern one is going to make it. fingers crossed!
 
MolaKule said:
Are you sure the prior fluid was Dexron VI or the original OEM LV HP?
Click to expand...

No, I am not sure - I only know the applicable TSB references Dex VI as the fluid being swapped out, but that TSB and an accompanying older one cover a number of model years, and I really have no clear way of knowing what's in my trans right now.
 
Got an appointment tomorrow morning to have the trans flushed with GMs procedure and the blue label M1. Will report back.
 
You will never hear the truth told about the history of the shudder problem. GM keeps their screw ups closely guarded despite what Mary Barra said after the ignition lock fiasco "follow the money"
 
AngryScientist said:
18 Chevy Colorado V6/8-sp trans. 29000 miles.

Just developed the dreaded, well known shudder issue on light acceleration. There is a TSB out there to flush the trans with new Mobil 1 Synthetic LV ATF HP fluid; which allegedly corrects the issue in the torque converter clutch area if the wear is not too bad/caught early, it's a new torque converter if not.

Has anyone got any insight on why the older dex VI fluid caused problems that the Mobil product abover remedies or if maybe there is something even better to run in this trans to prevent shudder in the future?

This work is being done under warranty, so I'm just going to let them do it, but in the future i plan to drain refill every 30k or so and want the best fluid possible.
Click to expand...
If you have the 8 speed then it never came with Dex 6 as the fluid, that is only for the older 6 speed transmissions. The 8 speed came with the DEX LV HP fluid that was hydroscopic, which is why Mobil came out with the new "blue label" LV HP fluid to fix that. You should be able to get the fluid exchanged under TSB 18-NA-355 without any cost.

Had the hard 1-2 shift develop on my 18 Sierra 1500 shortly after I bought it, took it back to the dealer and had them perform the TSB. Haven't had an issue with it since and its been over a year and more than 10K miles.
 
Add LubeGard Shudder Shock. Used that stuff multiple times and it does very well. The transmission on our van was doing exactly the same thing we put that in and fixed. Guy at a transmission shop told us that at first we didn’t believe it would work but for $20 we gave it a try. Well it worked and we will continue to use it.
 
My family member is a transmission technician for Chevy. He tells me that the 8 speed RWD transmissions torque converters are about half the size of the previous 6 speeds. In his opinion this exacerbates the problems because the smaller torque converter has to do a lot more work.

Based on what I have heard, the transmission fluid change with the new Mobil blue label fluid is good for about 30k and then the shudder starts to come back. He has seen several GM vans with the 8 speed fail at around 95k-100k with unknown maintenance history. As long as you keep on top of getting the transmission fluid completely changed every 30k with the Mobile blue label fluid, you should be okay for the long haul.

I have a feeling that these transmissions are going to become a major pain for GM in the future. I'm certain that most people are not going to use the correct fluid and change it every 30k. I can't figure out why GM is still using this transmission instead of the 10 speed.
 
A real point of aggravation is that there is no drain plug for the trans. On my honda van, which is also hard on trans fluid, I just drain the contents of the pan and refill every other oil change and that keeps the fluid fresh and happy. My plan for this is going to be an extraction pump to do the same and keep the fluid in good condition.
 
Jmlo96 said:
My family member is a transmission technician for Chevy. He tells me that the 8 speed RWD transmissions torque converters are about half the size of the previous 6 speeds. In his opinion this exacerbates the problems because the smaller torque converter has to do a lot more work.

Based on what I have heard, the transmission fluid change with the new Mobil blue label fluid is good for about 30k and then the shudder starts to come back. He has seen several GM vans with the 8 speed fail at around 95k-100k with unknown maintenance history. As long as you keep on top of getting the transmission fluid completely changed every 30k with the Mobile blue label fluid, you should be okay for the long haul.

I have a feeling that these transmissions are going to become a major pain for GM in the future. I'm certain that most people are not going to use the correct fluid and change it every 30k. I can't figure out why GM is still using this transmission instead of the 10 speed.
Click to expand...
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.
 
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