I have a 2024 c8 z06. It has 13K miles on it and I do beat on it pretty hard with maybe 75-100 launches I would say and 3/4 dragstrip days. I also have sprayed nitrous 7-8 times briefly to which it developed clutch slip requiring a clutch pressure controller from peitz performance which fixed that. It has every bolt on available at this time that I am aware of. The DCT started doing some weird things prior to the pressure controller when in auto like not shifting into 4th or 5th gear under WOT occasionally (maybe 1 out of 20 times) . I started manually shifting and that stopped and went away. Since then no shifting issues as long as I was in manual mode. I changed my dct filter at 7500 and at 10K miles. I did not goto dealer since I have depinned the tcm harness and used nitrous which should void my warranty amongst the other mods. Plus I have a hatred for dealers from past experiences that include door dings , curb rash, paint issues while there and even techs taking my car and having intercourse w females inside the vehicle (in the past not this car). So I avoid dealers at all cost. I am moderately mechanically inclined and have good tools from years of working on cars and have experience in the past actually rebuilding 700r4 and 4L60e transmissions but that was 20 years ago. (Not for career just for myself because I kept destroying transmissions with nitrous and could not afford to pay someone to fix it at that point in my life. )

A few weeks ago I was driving and got the dreaded rear axle off and service transmission warning. I turned it off and back on and it acted normal so I drove home. Before arriving home it did it again this time hanging in fourth gear. I coasted into driveway and then the car would not move . Checked codes and had a p0700 and p0868 and a p0867 code amongst others. I waited a few days reset and tried the transmission flush procedure x2 without success (bought the launch tool to do so, 500 bucks).




After reading on the forums it sounded like the valve bodies mainly the primary one were the culprit in a lot of cases and GM usually tries those next . So I bought one locally along with a new main filter and service filter and some dct fluid (chose valvoline due to price in case this didn’t work.) I have the service manual so I understood what I needed to do and it didn’t look too awful and at 2200 bucks vs a new transmission I figured worth a shot.

long story short replaced valve body, changed filters and fluid and it’s acting fine now w around a 100 miles. The fluid that came out was awful. It was full of what I feel like clutch debris but no big metal chunks but some small ones in the main filter






















I also did a video of the install in case others might be out of warranty and hit w the same problem I had and want to gamble on this. Now it’s absolutely possible I have the same issue in a few hundred miles but so far it’s back to stock shifting and feels normal.

there are a lot more details below if you want to know the process as I learned a lot. It’s probably a 6/10 difficulty mainly due to learning how to navigate the launch tool and do the flush and transmission fast relearn.

initial fix attempt here the flush


Maybe this helps someone.

 

I stumbled upon your YouTube video last night regarding how you changed the valve body. I have been a mechanic for decades, never swapped a valve body. Customer cars with transmission issues simple were sent to a transmission specialist shop. However, I would be surprised if there were more than a small hand full of trans shops who would be willing to take on a DCT rebuild or even a repair as you did. Unfortunately, we are stuck with going to a dealer or rolling the dice and taking it on yourself. Believe me when i tell you, the dealer tech is rolling the dice on a repair such as this as well. No way to know for certain, a valve body is the issue, until its done and tested. I feel your pain about taking cars back to the dealer for service. At least here on Long Island, most of them suck. Biggest problem with them is their techs having to perform the work according to book time. You had some ***** to take this on . So glad it is looking promising. Keep us posted on progress.

 

I also watched your videos yesterday. Very impressive. Even I was glad that it is working now.
The one thing that I didn't understand is the fluid and contaminations. It didn't seem so bad, but if it was, why doesn't the filters catch it?
Maybe the filters should be improved!

Great documentation, videos, explanations,.... Thanks

 

Thanks for the videos. Very informative.

 

I’m wondering if the material is too fine for it to catch or is bypassing somehow somewhere during certain conditions.

I’m going to see what blackstone says on fluid analysis and I’m gonna reach out to companies that rebuild valve bodies and maybe send them mine.(got this idea from a comment it’s not original to me) Between these two maybe can figure out what actually failed and why it failed . I’m sure GM already knows this answer but it’s not public knowledge so I wanna try to figure it out. Some forum members I bet know as well.

2020 cars are now out of drivetrain warranty and I can’t imagine spending 20K on a DCT swap is gonna sit well with owners and likely severely hurt resale value for us all if we can’t find a cheap solution to this problem. It’s starting to seem common.

 

My '24 2LT threw a few codes a couple months ago but was driving just fine. Brought it to my dealer and they said it was throwing valve body codes.
P0700
P2817 (valve body)
P2818 (valve body)
C2A19
U164F
I already knew this through my scanner buth there were no hiccups under normal or WOT conditions. I also had the "rear axle system off" message. They just decided to replace the valve bodies and no CEL's since. I enjoyed your vid though. Very informative.

 

When system components are designed they are required to have a certain contamination tolerance. And when filtration systems are designed they are required to meet that criteria. While your dark fluid could have been due to suspended particulates that were small enough to pass through the filtration system it could also be from chemical discoloration.

I suspect your discolored fluid was caused by excess clutch slippage so it could be either. There may be a clutch pack rebuild in your future. And if your analysis results comes back with large size particulate contamination it doesn't mean that it was getting past the filter since the sample was collected prior to passing through the filtration system.

I agree it would be great information to understand what is causing the valve bodies to have problems. And just to make sure you are aware, the canister filter filters from the inside out so you need to inspect the interior side of the media for contamination.

 

I also watched your video. I'm sorry to see you have this issue. You do run her fairly hard though and accelerated wear should be expected of the 'clutch' material. I also thank you for pointing out that the fluid in the CDT is shared with the diff. That's interesting. I'm not sure I like that either.
I wonder if the lab can identify what elements/materials are present in your fluid sample? That is to say did the particles come from the DTC clutch pack or the diff clutch pack? Or both?

A thought crossed my mind. I'm old so forgive the following:
I had a LT-1 vette back in the late 70's. I bought it used & it was a refugee from SCCA B/spt. prod. locally in the NY metro area. I was young and very ignorant. I didn't know I bought a used race car, that's how ignorant I was. My bud was a real mechanic and took pity on me and taught me how to work on cars by using my vette as the classroom. Took me 2 years, but I rebuilt every mechanical system in the car. Everything was used up. It also had some stuff that the factory didn't put on the car as it was a factory A/C car. Any way the owner's manual said this about two things that get abused very much when you race. Change the trans & diff fluids after each outing if the car is raced/ if not an M22 gets fluid every 6 mos./or 6k miles, same for the diff.

I wonder if the fluid change intervals and the filter change intervals are not short enough? I also wonder is there a way to add a bigger cooler (maybe not needed?) and an external filter instead of relying on just the OEM filters?
I'm subbing to this thread as I bought my '21 SR used, so no warranties for me. I have my own thoughts on what the fluid & filter schedules should be just going by what I've done with my two previous vettes.
I hope the valve body r&r solves your issue. JMHO, I don't see why it will not judging by the looks of your fluid & main DCT filter. Those were way sad looking.

Tom

 

You got your money out of the transmission you might try a salvage yard [one with a network] for a low mileage wreck that the trans is good

 

thanks for the info I will cut the material open and look at it. Good point on the fluid analysis I did try to catch after it had come out a bit as the first little bit would probably be excessively sedimented w material. My mind keeps thinking quicker fluid changes may go a long way in circumventing this issue.

 

sounds like we learned similarly, cept my teacher was my grandfather yelling at me to hold the light better and to pick up the 3/8 ratchet and hand it to him. lol. I remember to this day sayings like “that’s a pressurized peanut and a may pop, may pop now may pop later but will eventually pop” talking about old Chrysler turbo four cylinders.

im with you in that I think service interval decreases in timeframe I bet alleviates a lot of this problem for most people. BUT the guys that have it happen at 500 miles and 2K miles it doesn’t explain what happened w them. A bunchhhhh of people have reached out and told me they have had this issue some of them MULTIPLE times. Seems like a huge money drain for GM and tremec I can’t help but wonder how tremec makes any money given they originally just changed the transmission the first few model years before they allowed VB servicing at the dealers.

 

the used market for our cars as far as transmissions was not that bad. The stingray ones were like 4/5K used and z06 6-7 K used and there were a lot of them. Some in engine fires. Some from accidents. Some needed something small like a connector that broke or like a new side valve body cover, etc. if I have full failure I’m probably gonna just going to go used from a wrecked car since I know it was probably working prior to that. Most of the salvage places offer 30 day guarantee if installed by a shop.

this is all promising as well and makes a 2K valve body seem like an expensive gamble compared to a whole used trans for 5K or so.

 

A majority of the people that follow the GM recommended schedule don't have any problems. If it is a case that the change intervals are insufficient then why don't they have problems? And the longer you go without a problem the less likely you are going to have a problem. The problems are most likely quality control problems and not a problem of contamination getting past the filtration system and causing a problem.

 

Great videos, thank you! It takes time to do them and a PITA sometimes.

I haven’t followed very many transmission posts because most are just complaining with no real solutions. It’s nice to see a post with possible solutions as more cars age past BTB warranties.

I definitely will be watching for lab results and if the fix worked for an extended time.