Well, I got started on the Nextgen kit in my 2023 6.2 Denali pu. I'm retired, so I just worked about half a day on Sat and Sun. The exhaust is a pain in the ass. My PU just turned 17,000 miles and the exhaust nuts came off with a half inch break over and no studs broke. I live in Texas, so the underside was clean and no rust. I got everything back together Sun afternoon and was about to put the transmission fluid in. I dumped the old fluid, which was real clean and the magnets in the pan were real clean, and saw a kind of a two holer O ring thing. I hadn't seen it before or even in some pictures in the manual. Never the less, I pulled the exhaust back off and removed the valve body again. I'll get new bolts again today and start again tomorrow. And it is hard to hold up and start the wiring harness plug in and get the shift lever, that's not what is is, but you have to put a lever back into a thing on the aux valve body. It's kinda hard to get in with out knocking off the O ring thing thats on top of the valve body. I'll report back when finished.
Project Carbon Next Gen 10 Speed Valve Body Kit - Finally Installed!
- Thread starter jfoj
- Start date
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Sorry to hear that O-ring caught you off guard. Sux needing to drop everything again. Good news, is the 2nd time is usually faster and easier. Suggest you load the exhaust manifold studs with Anti-seize, prefer the copper for exhaust, so if you ever need to deal with dropping the exhaust to change a transmission filter in the future you can have some luck hopefully not breaking any exhaust studs.
Do not worry about trying to get the transmission fluid up to 176F to verify it is full. 100-120 F is fine. Then check it again in a few days once you have had a chance to drive it on the highway to fully fill all the clutch packs.
Also suggest you wipe the bottom rail of the transmission where the gasket goes with brake cleaner or something to get all the transmission fluid off the gasket mating surface. Also spray the gasket clean of any trans fluid. This makes for a better leak proof seal for the pan gasket IMHO.
Do not worry about trying to get the transmission fluid up to 176F to verify it is full. 100-120 F is fine. Then check it again in a few days once you have had a chance to drive it on the highway to fully fill all the clutch packs.
Also suggest you wipe the bottom rail of the transmission where the gasket goes with brake cleaner or something to get all the transmission fluid off the gasket mating surface. Also spray the gasket clean of any trans fluid. This makes for a better leak proof seal for the pan gasket IMHO.
I finally got my nextgen kit installed. The kit I bought did not have the 6 shift valves. My valve body had 5 balls on one side and 3 balls on the other side. and 2 in the aux. valve body, just like jfoj's. I had exactly the same parts left over as jfoj's did. My truck shifted good to start with. I think it shifts a little harder and when coming to a stop, it down shifts better, I think. I've only put about 10 miles on it. The old feed limit low and high valves looked brand new, I don't know if I would have any problems down the road or not. I used 14 qt. transmission fluid, ULV. The biggest problem I had was getting the valve body in and lined up and hooked up at the same time while on your back. If I notice anything after a few miles, I'll let ya know.
@Rbock8
Glad you finally got everything back together and working. Sounds like you had about the same amount of fluid I ended up using, I know I used at least 13 if not 14 Quarts. I would have to go back and see how many Quarts I used out of my additional 12 pack and how much was left in my pump tank to be 100% sure.
You should get some miles on the vehicle and then recheck the fluid level just to make sure you are topped off. Also report back once you get 3-4k miles on the update on how things are working out.
You should feel the upshifts are slightly firmer, not harsh, not slippery, just precise and slightly obvious. Down shifts should be clean as well. I found that the original valve body configuration was not precise, had hunting, flares and sometimes an occasional harsh shift out of nowhere. This was pretty much in the 2-4 or maybe 2-5 upshifts and downshifts.
At 8400 miles when I update my valve body, most valve looked good, not much for wear. But glad I did the update and the aftermarket pan with the drain, with the fluid from Rock Auto being reasonably priced, I will drain the trans and refill either every other or every 3rd oil change. This will only get about 1/3-1/2 the fluid out, but I figured I an in no hurry to want to drop the exhaust to replace the filter, so I will just keep draining and filling the pan every 7500-10,000 miles, this along with the valve body update, should hopefully keep the 10 speed alive for many miles.
Glad you finally got everything back together and working. Sounds like you had about the same amount of fluid I ended up using, I know I used at least 13 if not 14 Quarts. I would have to go back and see how many Quarts I used out of my additional 12 pack and how much was left in my pump tank to be 100% sure.
You should get some miles on the vehicle and then recheck the fluid level just to make sure you are topped off. Also report back once you get 3-4k miles on the update on how things are working out.
You should feel the upshifts are slightly firmer, not harsh, not slippery, just precise and slightly obvious. Down shifts should be clean as well. I found that the original valve body configuration was not precise, had hunting, flares and sometimes an occasional harsh shift out of nowhere. This was pretty much in the 2-4 or maybe 2-5 upshifts and downshifts.
At 8400 miles when I update my valve body, most valve looked good, not much for wear. But glad I did the update and the aftermarket pan with the drain, with the fluid from Rock Auto being reasonably priced, I will drain the trans and refill either every other or every 3rd oil change. This will only get about 1/3-1/2 the fluid out, but I figured I an in no hurry to want to drop the exhaust to replace the filter, so I will just keep draining and filling the pan every 7500-10,000 miles, this along with the valve body update, should hopefully keep the 10 speed alive for many miles.
I've got 500 miles on the Next Gen kit and everything is good. The up shifts and the down shifts are all better than before, and I thought they were fine to start with. I did put the aluminum pan on so I could change the transmission fluid. I did mine at 17000 miles and the fluid was still red. I think I'll go 15000 or 20000 miles between changes. Before with only highway driving, the trans temp would run about 145, in town it would get to 165 or 170. On the highway now, it runs 135 and in town hasn't go over 150. I'm sure this will change with more stop and go traffic. But it is definently cooler than before.
Glad to hear you are up and running well at this point.
Kind of sad and funny at the same time GM has had to release a 3rd version valve body for these 10 speeds after 6 years. As I recall 2019-2021 had a 1st generation valve body, then somewhere between the 2021 and 2022 model year GM came out with the 2nd version valve body which we all have and a few of us have upgraded, sometime in the Aug/Sept of 2025 the 3rd version valve body was released for service replacements and I assume for installation in the 2026 model year. This 3rd version valve body is a big redesign with many changes based on info I have seen.
Kind of sad and funny at the same time GM has had to release a 3rd version valve body for these 10 speeds after 6 years. As I recall 2019-2021 had a 1st generation valve body, then somewhere between the 2021 and 2022 model year GM came out with the 2nd version valve body which we all have and a few of us have upgraded, sometime in the Aug/Sept of 2025 the 3rd version valve body was released for service replacements and I assume for installation in the 2026 model year. This 3rd version valve body is a big redesign with many changes based on info I have seen.
Meant to post this earlier, this is info on GM's 3rd generation 10 speed valve body that they redesigned and released. The long delays for valve bodies a few months ago may have been due to the 3rd design being in the works? Not sure when this version valve body will hit "New" vehicles, but the timing is such that possibly the 2026 models may have started with this latest version valve body?
I believe the first generation valve bodies were in the 2019-2021 models. Sometime either late 2021 or with the beginning of the 2022 model year the 2nd generation valve body was released, this 2nd generation valve body seemed to have the highest number of failures, but then maybe for 2022-2024 they sold more of the trucks with these 10 speeds? Then we now have the 3rd generation valve body due to all the previous problems. Hopefully this latest version is more reliable.
No idea if the 3rd version is directly backward compatible without and programming, assume this info will find its way out onto the interwebs at some point.
Anyway, interesting that this seems to be a pretty radical change where GM may have eliminated some parts/functions within the original valve body footprint.
I believe the first generation valve bodies were in the 2019-2021 models. Sometime either late 2021 or with the beginning of the 2022 model year the 2nd generation valve body was released, this 2nd generation valve body seemed to have the highest number of failures, but then maybe for 2022-2024 they sold more of the trucks with these 10 speeds? Then we now have the 3rd generation valve body due to all the previous problems. Hopefully this latest version is more reliable.
No idea if the 3rd version is directly backward compatible without and programming, assume this info will find its way out onto the interwebs at some point.
Anyway, interesting that this seems to be a pretty radical change where GM may have eliminated some parts/functions within the original valve body footprint.
Buckshot85
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How much easier would the job be, besides the exhaust, if you used the entire valve body assembly Next Gen sells instead of doing the kit? Would the check balls still have to be messed with? I imagine it would certainly speed up the install?
Clearly an entire valve body would be simpler and speed things up a little bit, however, the NextGen valve body pricing is crazy high. I don't recall the exact number but I think it was like $3,500+. The valve body disassembly and part installations really not that bad, If you take your time and pay attention to details. Since most people will be doing the work on a operational transmission that hasn't really worn out and likely does not have a dirty, debris filled valve body, they probably will do what I did which was just replace one valve at a time rather than disassemble the entire valve body and hundreds of pieces and then try to reassemble it.
The biggest problem with the check balls is there are no good pictures online. I unfortunately didn't get pictures of the two check balls that were on the back side of the small auxiliary valve body, but you can figure out where they belong without too much concern. And while GM is on to its 3rd version valve body, most of us won't see anytime soon, if you're not careful, there could be inconsistent information out there on the web. Even the manual i purchased primarily had pictures and information for the first version valve body that GM put out between 2019 android 2021.
I think there may be a transmission shop that NexGen has partnered with where you can send your valve body and have the kit installed probably cheaper than the entire NexGen replacement valve body..
I have experience rebuilding and repairing automatic transmissions, while this was not a core part of my past, I have worked on a variety of automatic transmissions so I had no concern of my abilities
The biggest problem with the check balls is there are no good pictures online. I unfortunately didn't get pictures of the two check balls that were on the back side of the small auxiliary valve body, but you can figure out where they belong without too much concern. And while GM is on to its 3rd version valve body, most of us won't see anytime soon, if you're not careful, there could be inconsistent information out there on the web. Even the manual i purchased primarily had pictures and information for the first version valve body that GM put out between 2019 android 2021.
I think there may be a transmission shop that NexGen has partnered with where you can send your valve body and have the kit installed probably cheaper than the entire NexGen replacement valve body..
I have experience rebuilding and repairing automatic transmissions, while this was not a core part of my past, I have worked on a variety of automatic transmissions so I had no concern of my abilities
Buckshot85
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Thanks, Guys. Great info in this thread.
Well done.
Well done.
I am going to post a set of valve body pictures below with the 10 check balls circled for easier identification. There are actually more than 10 check balls in this valve body, but the additional check balls are captive with a pressed in top sheet metal retainer that should not be removed. Leave the captive check balls as they are. I did not mark the captive check balls, but if you know what to look for, you can find them.
These pictures are for a Version #2 valve body for a 10L80/10L90 with the electronic push button or electronic column shifter used primarily between 2022-2025. Note there was a Version #1 valve body used between 2019 and 2021 which is different and may not have the same number and placement of check balls. The 10L1000 "Allison" transmission valve body used in the 3/4 ton and up trucks is similar and uses many of the same parts but I think is also slighter larger as well. Most of the 10L1000 transmissions also use a cable shifter with a manual shift valve and do not have 2nd electric fluid pump because the 3/4+ ton trucks do not have the ASS system (Auto Stop/Start) As of late 2025 a Version #3 valve body has been released for service replacements and may have been installed in some of the very late 2025 vehicle builds. I assume this Version #3 valve body will be used going forward into 2026+ vehicles unless there is another updated valve body released. So just be aware the valve body is a moving target, has evolved and has a number of variations with different numbers of check balls depending on the valve body configuration as well if the shifter is an old school manual cable operated shifter or a newer electronic push button or column shift like in the 2025 1/2 ton models.
All this said, here are pictures of a 2024 Version #2 valve body with electronic push button shifter with 10 check balls clearly identified. The good news with this 3 section valve body with the separator plates and the primary separator plate that has a 2 retainer bolts, you can drop the check balls in the valve body sections without using Vaseline or transmission assembly lube and then install a separator plate and flip the valve body section without the check balls falling out. The biggest trick you need to figure out is properly aligning the larger separator plate so the alignment roll pins will pass through the separator plate and into the other valve body section. I used a tapered punch to align the roll pin holes in the valve body section and separator plate. You could use some tight fitting bolts or even some similar size roll pins, but I had good luck with a single tapered punch, aligned 1 hole, snugged one of the separator plate bolts, aligned the other hole, snugged the other separator plate bolt, then double checked with the tapered punch and by eye that the valve body and separator plate holes were aligned, then torqued the 2 separator plate retaining bolts. Sound more complicated than it really is, just take a moment to get these 2 roll pin alignment holes with the large separator plate and all will be good. You WILL KNOW very quickly if these holes are not aligned when you try to mate the 2 larger valve body sections. The issue should become very obvious.
The 4th picture with the "Picks" pointing to areas within the lower valve body half are accumulator pistons that could fall out. Some have springs under them. Pay careful attention to these and do not flip this portion of the valve body over otherwise you will have more guesswork to deal with. The larger piston is the TCC Accumulator and is replaced as part of the NextGen update kit with a machined steel piston rather than the anodized aluminum piston.
The 5th picture is fair warning about locating and making sure you find and place the valve body to transmission case double O-ring or figure 8 gasket back in top of the valve body before you lift it back up to install in the transmission. This gasket can fall into the transmission drain pan and only be found when too late. Wish I would have noted this previously as it may have saved some from this . I reused the original gasket because it is not included in either the NextGen kit or part or the filter kit. Also make sure you have the filter O-ring and this is installed where the filter neck is inserted into the transmission.
The last pictures and video are of the transmission filter O-ring gasket that needs seal the neck of the filter where is is pushed into the transmission pump body. Make sure you find this round gasket, lube it and install it into the transmission housing before you replace the transmission filter.
Anyone that does not want to update their Version #2 valve body, could consider swapping in the Version #3 valve body, BUT I believe this would require specific TCM programming for the shift solenoid values. I believe the Version #3 valve bodies will work in transmissions with Version #2 valve bodies and may actually be even cheaper than the Version #2 NextGen kit with full shift valve, BUT who knows if GM actually is using thicker separator plates without the paper gaskets?? The GM version #3 valve bodies may not be significantly better than the non modified Version #2 valve bodies.
Good luck to anyone doing this job, it is not as bad as it may seem if you take your time, take pictures and make notes as needed and keep the bolts organized. I used a cardboard template to place the bolts in so I did not need to spend time figuring out what bolts went in what location.
These pictures are for a Version #2 valve body for a 10L80/10L90 with the electronic push button or electronic column shifter used primarily between 2022-2025. Note there was a Version #1 valve body used between 2019 and 2021 which is different and may not have the same number and placement of check balls. The 10L1000 "Allison" transmission valve body used in the 3/4 ton and up trucks is similar and uses many of the same parts but I think is also slighter larger as well. Most of the 10L1000 transmissions also use a cable shifter with a manual shift valve and do not have 2nd electric fluid pump because the 3/4+ ton trucks do not have the ASS system (Auto Stop/Start) As of late 2025 a Version #3 valve body has been released for service replacements and may have been installed in some of the very late 2025 vehicle builds. I assume this Version #3 valve body will be used going forward into 2026+ vehicles unless there is another updated valve body released. So just be aware the valve body is a moving target, has evolved and has a number of variations with different numbers of check balls depending on the valve body configuration as well if the shifter is an old school manual cable operated shifter or a newer electronic push button or column shift like in the 2025 1/2 ton models.
All this said, here are pictures of a 2024 Version #2 valve body with electronic push button shifter with 10 check balls clearly identified. The good news with this 3 section valve body with the separator plates and the primary separator plate that has a 2 retainer bolts, you can drop the check balls in the valve body sections without using Vaseline or transmission assembly lube and then install a separator plate and flip the valve body section without the check balls falling out. The biggest trick you need to figure out is properly aligning the larger separator plate so the alignment roll pins will pass through the separator plate and into the other valve body section. I used a tapered punch to align the roll pin holes in the valve body section and separator plate. You could use some tight fitting bolts or even some similar size roll pins, but I had good luck with a single tapered punch, aligned 1 hole, snugged one of the separator plate bolts, aligned the other hole, snugged the other separator plate bolt, then double checked with the tapered punch and by eye that the valve body and separator plate holes were aligned, then torqued the 2 separator plate retaining bolts. Sound more complicated than it really is, just take a moment to get these 2 roll pin alignment holes with the large separator plate and all will be good. You WILL KNOW very quickly if these holes are not aligned when you try to mate the 2 larger valve body sections. The issue should become very obvious.
The 4th picture with the "Picks" pointing to areas within the lower valve body half are accumulator pistons that could fall out. Some have springs under them. Pay careful attention to these and do not flip this portion of the valve body over otherwise you will have more guesswork to deal with. The larger piston is the TCC Accumulator and is replaced as part of the NextGen update kit with a machined steel piston rather than the anodized aluminum piston.
The 5th picture is fair warning about locating and making sure you find and place the valve body to transmission case double O-ring or figure 8 gasket back in top of the valve body before you lift it back up to install in the transmission. This gasket can fall into the transmission drain pan and only be found when too late. Wish I would have noted this previously as it may have saved some from this . I reused the original gasket because it is not included in either the NextGen kit or part or the filter kit. Also make sure you have the filter O-ring and this is installed where the filter neck is inserted into the transmission.
The last pictures and video are of the transmission filter O-ring gasket that needs seal the neck of the filter where is is pushed into the transmission pump body. Make sure you find this round gasket, lube it and install it into the transmission housing before you replace the transmission filter.
Anyone that does not want to update their Version #2 valve body, could consider swapping in the Version #3 valve body, BUT I believe this would require specific TCM programming for the shift solenoid values. I believe the Version #3 valve bodies will work in transmissions with Version #2 valve bodies and may actually be even cheaper than the Version #2 NextGen kit with full shift valve, BUT who knows if GM actually is using thicker separator plates without the paper gaskets?? The GM version #3 valve bodies may not be significantly better than the non modified Version #2 valve bodies.
Good luck to anyone doing this job, it is not as bad as it may seem if you take your time, take pictures and make notes as needed and keep the bolts organized. I used a cardboard template to place the bolts in so I did not need to spend time figuring out what bolts went in what location.
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Great info in this thread. Thanks OP. I too installed a VB kit from NextGen complete with steel billet valves. I also added a thermostat bypass valve from PPE on my 2022 LM2 w/10l80. Truck had only 30k miles and the fluid was pretty clean and there were no bad symptoms prior to the upgrade. Now transmission shifts are more pronounced, but not harsh and I attribute it to removed dampeners. These are the only upgrades I did. Everything went smoothly, however my only concern is the operating temperature of the transmission didn't really change much. In stop and go traffic I used to seeing around 195F and perhaps up to 205F. On a steady highway drive it usually hovers around 176-182F depending on an ambient temperature. After the upgrade temperatures are somewhat the same. It might be taking just a bit longer to get to those temperatures, but nonetheless transmission temperature gets there on a regular basis. I used Amsoil ULV fluid. I understand that adding a deeper pan would likely bring the overall temperature down, however I was thinking with adding a bypass valve I would also see a reduction in temperature as well. Has anyone else encountered the same thing without performing additional cooling upgrades?
@x4rang
I cannot say I have first hand info on the Diesel with the external cooling loop thermostat, I do know they typically run hotter than the the gasoline counterparts, somewhere typically around 200F as I recall. I believe a number of users here have performed similar upgrades on their Diesel's and I think with the PPE bypass valve?? Maybe they can chime in, however, I am pretty sure any of the Diesels with the bypass valve had the operating temps probably drop down to at max around 165F??
I will search around and see if I can find any comments from folks that changed/removed the external cooling loop thermostat.
You may also want to look at this Reddit post and note what the person said about having to machine the plug for where the plug went where the gasoline thermostat is located in the valve body. I have no first hand experience on this issue as I have only worked on the gasoline vehicle valve bodies.
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I cannot say I have first hand info on the Diesel with the external cooling loop thermostat, I do know they typically run hotter than the the gasoline counterparts, somewhere typically around 200F as I recall. I believe a number of users here have performed similar upgrades on their Diesel's and I think with the PPE bypass valve?? Maybe they can chime in, however, I am pretty sure any of the Diesels with the bypass valve had the operating temps probably drop down to at max around 165F??
I will search around and see if I can find any comments from folks that changed/removed the external cooling loop thermostat.
You may also want to look at this Reddit post and note what the person said about having to machine the plug for where the plug went where the gasoline thermostat is located in the valve body. I have no first hand experience on this issue as I have only worked on the gasoline vehicle valve bodies.
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StephenPT
Full Access Member
You shouldn't be seeing anything near 200F with the PPE thermostat bypass installed. The OP of the reddit thread JFOJ posted above said he couldn't get the trans temp above 130F at 84F ambient. Demonworks on YouTube had similar results -
Did you deal with this issue when working on your valve body?
JFOJ did his upgrade on a 6.2 gas engine, but it sounds like the Next Gen kit does a poor job of addressing the differences between gas/diesel, model year changes, etc. and providing the right parts or documentation on how to deal with the differences.
Starting to wonder if in the 10 speed Diesel valve bodies, if you upgrade them, just leave the valve body thermostat area alone?? Seems on the Diesel valve body the internal thermostat is already bypassed because of external thermostat in the cooler line. I need to reread the update instructions and see if there is anything special going on with the internal valve body thermostat other than removing the "pill" or thermostatic element and flipping the "pill" holder.
@StephenPT - Yes, I had to use a local machine shop to precisely shave off 0.265" from that end plug, and had it installed according to NextGen’s instructions. From watching that video you linked, at the beginning Greg mentions that his truck had a transmission cooler installed (however, I'm not sure if it's the PPE aftermarket one or if he is referring to a standard OEM cooler). Some people in the comments under that video also mention that having only a bypass valve installed hasn't tremendously affected their transmission temperature. I'm questioning why the NextGen kit hasn't brought any noticeable reduction in the temperature I'm observing.
Maybe someone, after reading this excellent thread, could share any insights on how much of a temperature drop they are seeing with a diesel engine after NextGen valve body upgrade (with or without any additional mods).
Maybe someone, after reading this excellent thread, could share any insights on how much of a temperature drop they are seeing with a diesel engine after NextGen valve body upgrade (with or without any additional mods).
