r/gmcsierra • u/Jermi321 • Apr 10 '25

🔧Performance Upgrades 🔧 Next Gen Drivetrain Project Carbon Valve Body Upgrade

https://nextgendiesel.com/collections/10l80e-valve-bodies/products/project-carbon%C2%AE-10l80-e-diy-valve-body-upgrade-kit-v3-1?variant=44018016157869

Has anyone proactively installed the Next Gen Drivetrain valve body upgrade kit? GM's software update does nothing to address the root cause of the 4th clutch auto engagement issue. It is a valve body mechanical wear issue causing fluid to bypass the valve causing an inadvertent 4th clutch to engage simultaneously with the other 3 clutches causing the transmission output shaft to lock up. The Next Gen kit is advertised as a mechanical solution to the shift valve wear issue.

I have noticed on several trucks that the fluid is damn near black at 45,000ish miles. My impression is if the valve body wear is gradual, then maybe over time the fluid leaking by the shift valve is not enough in the beginning stages of wear to cause the clutch drum to fully engage, but rather enough is leaking by to cause the clutch drum to partially engage causing a clutch slippage issue which is causing the fluid to look burnt in such a short time frame. I am looking to proactively take care of the issue GM will not. Truck has 3800 miles on it and I cannot afford to be without it for months at end.

TLDR: Thoughts on installing the valve body upgrade as a failure prevention upgrade.

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u/Jermi321 Apr 14 '25 edited Apr 14 '25

Thank you for your detailed and informative response. Sounds like you and I are of a similar mindset about GM's resolution and how to go about curing the issue.

What is your take on adding the shift valves in addition to the kit? During your conversation with Next Gen, did they explain to what their experience with shift valve bore wear? I would be more inclined to add the shift valve spools if I had a more detailed and informative explanation for the need. Is the need purely because of bore wear, or did the Next Gen engineers actually change the geometry of the valve spools. .

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u/Choice_Leader_8213 Apr 14 '25 edited Apr 15 '25

What the Next Gen guy conveyed is in the years of rebuilding transmissions they took what worked and did not have problems from other manufacturers was considered. They also wanted to try to offer a solution for under $1k for a solution. So they balanced the option of the making the kit with the shift valves but that ran the cost up because the valves are not cheap to produce. After discussions and my plan to hopefully keep the Yukon for some period of time, plus I would be pulling the valve body anyway, I would spend the additional money for the valves because they pretty well convinced me that the shift valves would be the best option to reduce/eliminate valve body bore wear. To my understanding there was not any specific change in the valve design.

A few notes, I questioned Next Gen about fluid fill and bringing the trans temp up to the 200+ range and was told this is really not necessary, easier to fill cold, start engine, make sure fulid it topped off, allow engine to run and fluid to warm up to around 100-120F with plug out and allow any fluid expansion to drip out, then install plug, typically while engine is running. Then maybe check a few days later to make sure level is still good. Trying to check fluid with temps over 200F is dangerous.

The other thing is some of the bolts are torque to yeild, one use bolts. I think for the filter and there are also some bolts that have a special sealer on them that if not replaced may cause internal fluid leakage and low pressure to some of the clutch packs. Still looking for more info on this but have ordered this bolt kit GM Part #24050764 which superceded GM Part #24294356.

https://www.youtube.com/watch?v=XwDzWnwAiuk

https://www.youtube.com/watch?v=d0Tm5OlOYuE

I have also being doing many things to counter the 6.2l failure to include DFM and Auto Stop/Start bypass, running 5W30 or 0W40 engine oil, running 9 quarts with filter change, 8 quarts is about 2/3 quart low on these engines, installing a magnetic oil drain plug, changing the oil when the OLM hits 50%, adding a Catch Can and not allowing the engine to warm up at idle.

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u/Jermi321 Apr 14 '25

Makes perfect sense thinking of it that way. If the other valves are wearing out bores, then stands to reason the shift valves would also wear their respective bores.

I have added the Range module to my truck already and am quite happy with it. I understand it doesn't fix the lifter problem, but now it runs like it is supposed to. It also deleted the Auto Stop/Start as well. I have been looking into the RXP catch cans and am going to be installing one on the truck as well.

I changed the factory fill oil at 693 miles and just changed the oil again at 3,628. I will send the truck in for it's "free" service at 7,000. Then, change the oil, trans fluid and filter, differentials fluid, and transfer case fluid at 10,000. This is when I will be pulling the valve body and adding the Next Gen components. After that, my plan was to change the oil at 5,000 mile intervals and do oil analysis to confirm that interval. I also have the 6.2L

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u/Choice_Leader_8213 Apr 14 '25

I have the Range Module as well. It still have the valves being disabled under Decel With Fuel Cutoff (DFCO), but at least the count is far lower and less frequent then without the module. You can run the transmission in L9 up to around 55-60 MPH and it will cause all DFM to not function.

I went with the JL Catch Can, works fine, chose this due to the mounting ease with bracket and proper length hoses with correct connectors. 15 minute job installing.

Oil has been change 3 times in 6k miles. Running Pennzoil Ultra Platinum in the engine now. Mainly because of the Moly content (for lifter needle bearing and engine bearing protection). While this is NOT GM Dexos licensed, it has very low Sodium which is the main thing Dexos wants out of the oil. The higher end oils generally will not/do not want to submit for Dexos approval because they are REQUIRED to turn over their oil formulation and due to intellectual property and the licensing fee they choose not to. I am not worried about not running a Dexos approved oil that I know that the sodium level of the Pennzoil Ultra Platinum is pretty much the same level as any Dexos licensed oil.

Thinking of putting a PPE transmission pan on the truck. Not really for the cooling or 2 extra quart capacity, but for the ease of draining the transmission. I could try to weld a bung in the factory pan, but figured I would just get a pan with a drain. This way I would be more inclined to perform a drain and fill every 10k or so. Far easier than removing the pan. Probably would pull the pan every 30k to clean and inspect for debris and change filter.

While the 10 speeds have other problems than the valve body, this is a primary problem with them. The pump drive gears are helical cut and can get noisy, this requires the trans to be removed, most shops put the straight cut Ford gears in which are a direct swap. There have been some problems with drum damage and piston/seal issues, but I believe some of this may have been aggravated by either low pressure and slippage or harsh engagement due to the valve body. Same with some of the torque converter failures. I think a number of these hard part problems also occur with more severe duty like towing and hauling heavy loads on a regular basis as well. The 6.2l has a lot of torque and I have not monitored the Tow mode much, but I think delaying the shifts under heavy loading is probably a good thing.

Post a picture of the trans pan when you pull it if there is anything to be seen and concerned about. I would hope at 10k if you have not noticed anything unusual, hopefully the trans pan and magnets will appear "normal". I believe if you catch the valve body problem and sort it out with a good solution early on you can clearly save the transmission from self destruction.

I did this with a VW 6 Speed Tiptronic a number of years ago that started with VERY harsh downshifting when the fluid was very warm around 70k miles. Pulled the pan and valve body for repair. Pan was VERY clean as I jumped on the problem early. This valve body I sent out to an independent trans shop that convinced me they had a solution for the problem. I think it cost me about $650 for shipping both ways and repair, but the problem was in fact corrected and ran the car another 45k miles before we sold it without a problem. So valve bodies are important and can cause premature transmission wear if not addressed early on.

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u/Choice_Leader_8213 Apr 28 '25

Parts are in, just need time now.

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u/Choice_Leader_8213 Apr 28 '25

Sonnax Torlon Replacement Check Balls

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u/Choice_Leader_8213 Apr 28 '25

PPE Aluminum Trans Pan with Magnetic Drain Plug, 12 lbs!

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u/Choice_Leader_8213 Apr 28 '25

PPE Pan Internal Baffling

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u/Choice_Leader_8213 Apr 28 '25

Some additional Sonnax parts, I may use some of these??

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u/Pretend-Category6934 Jun 23 '25

Disclaimer: new to reddit. 

I just installed the Next Gen 10L80 valve body kit with the steel relay valves, and B&M deep pan (its got a large magnet which is why I chose it, plus also had one on my TH400 and was great). 

The install was was mostly trouble free, but the instructions are lacking and showed pictures for some other version of the 10L80 than what I had. So there was has a fair amount of head scratching but I believe I installed it correctly as the tranny runs through all 10 gears minus a weird behavior today from 1-2, 2-3, but I only have about 30 miles on it. 

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u/Pretend-Category6934 Jun 23 '25

I'd post some pictures, but this shit is confusing. 

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u/Choice_Leader_8213 Jul 01 '25

https://www.tahoeyukonforum.com/threads/project-carbon-next-gen-10-speed-valve-body-kit-finally-installed.153898/

Proper fluid level setting is not clear, it is all over the place depending on what you are reading or watching on YouTube.

Readers digest version.

  1. Engine MUST be running when setting the final fluid level. You MUST put the fill plug back in the transmission while the engine is running.

  2. You may need to check the fluid 2-3 times after reassembling the transmission.

  3. Use the remote keyfob to start engine and shut it off, saves time and keeps the exhaust cooler so you will not get burned as easily.

  4. DO NOT brake torque or power brake the transmission to raise the temperature. If you remove the transmission thermostat you you can skip any attempt to raise the transmission temperature. If you still have the transmission thermostat installed, just make sure you check the transmission level after you fully warm the transmission up, even if it does not hit the 170F+ mark, even if you get the transmission temp to 150-160F you have probably forced the transmission thermostat open, so just recheck the fluid level after a good long drive.

  5. The TCM will also relearn over time while you drive after a repair.