NEXTGEN Drivetrain valve body swap

[JayRich]

What kind of issues did you have if I can ask? Was it the complete rebuilt VB or did you install their kit parts in your stock VB? Everytime I’ve called for tech assist and questions I’ve dealt with Tyler and he seems to be very knowledgeable. I was still having some hard downshift shift issues 5-4-3 downshift over 35 mph after the active relearn and my complete VB install. I had the fluid level verified and just did a Service Fast Learn TCM flash and about 500 miles into the Fast Learn and smoothing out on that 5-4-3 downshift now. Following this thread.

I originally installed their rebuild kit in my stock VB. Had issues with the "D" solenoid valve moving smoothly. Per their instructions I moved the valve manually until it seemed to move ok. Installed in truck. Had very hard and slow shifts but tried to drive for the learning process. After about 10 miles the truck downshifted hard getting off the highway and went into limp mode. Code was for solenoid D being stuck on. Cleared code and restarted truck, shifts were still very hard and then went back into mode, again solenoid D stuck on. After talking with Tyler I decided to go with their complete VB instead of fighting what could be a bad factory VB.

After receiving the new VB (which was completely clean and dry even though they claim its tested?) I swapped it. Truck acted the exact same way, except at that point almost every time it went into limp mode it was for a different solenoid. I changed fluid and filter the following day with the same result. Each time I read the codes I had one for almost every solenoid.

Mind you through all of this I was lucky to talk to NG once a day. I submitted all my info for warranty after finally talking with Logan. He said if I could get it shipped that day (6-23) they could get it back to me Friday (today, 6-26). According to UPS they received it yesterday morning and I have yet to get a response from either a call or email. I have sent them a message as well as left a voicemail.

 

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[R467X]

I originally installed their rebuild kit in my stock VB. Had issues with the "D" solenoid valve moving smoothly. Per their instructions I moved the valve manually until it seemed to move ok. Installed in truck. Had very hard and slow shifts but tried to drive for the learning process. After about 10 miles the truck downshifted hard getting off the highway and went into limp mode. Code was for solenoid D being stuck on. Cleared code and restarted truck, shifts were still very hard and then went back into mode, again solenoid D stuck on. After talking with Tyler I decided to go with their complete VB instead of fighting what could be a bad factory VB.

After receiving the new VB (which was completely clean and dry even though they claim its tested?) I swapped it. Truck acted the exact same way, except at that point almost every time it went into limp mode it was for a different solenoid. I changed fluid and filter the following day with the same result. Each time I read the codes I had one for almost every solenoid.

Mind you through all of this I was lucky to talk to NG once a day. I submitted all my info for warranty after finally talking with Logan. He said if I could get it shipped that day (6-23) they could get it back to me Friday (today, 6-26). According to UPS they received it yesterday morning and I have yet to get a response from either a call or email. I have sent them a message as well as left a voicemail.

I also spoke with Logan on 6-22. Shipped mine out the same day and it delivered on Wednesday morning. Yesterday afternoon I got a shipped notification and I just received it. I plan to install this tomorrow..hoping no more problems.

Did you also experience 4-5 second engaged delays when shifting from P to R and D?

 

[JayRich]

I also spoke with Logan on 6-22. Shipped mine out the same day and it delivered on Wednesday morning. Yesterday afternoon I got a shipped notification and I just received it. I plan to install this tomorrow..hoping no more problems.

Did you also experience 4-5 second engaged delays when shifting from P to R and D?

Yes, every gear was 3-5 seconds. LUCKILY the shop I am using is not in a busy place as the truck couldn't get out of a snails way. Best of luck with your new VB, I'm going to try to get ahold of Tyler again to see what my status is.

 

[R467X]

Yes, every gear was 3-5 seconds. LUCKILY the shop I am using is not in a busy place as the truck couldn't get out of a snails way. Best of luck with your new VB, I'm going to try to get ahold of Tyler again to see what my status is.

I found that calling them back to back over a period of 15 mins someone eventually picks up the phone.

Yeah I also got a violent jolt each time it changed gears and when I tried to go on a test drive it hit 2k rpm and a violent jolt. I came right back. I don't believe it's supposed to shift from P to R and D so violently. And I don't want to grenade that tranny

 

[Master Chief BT]

I received mine back in early December 2025 and had the NG VB installed by a transmission shop I use. There was a paper in the box that said DO NOT FLASH TCM (or something like that) let VB adaptive relearn new shift points. So I did that. A little rough at first but noticed each day it got better. I have about 8,000 miles on my NG VB with a couple to long haul toe runs with my Airstream. I took to a diesel custom guy here as Tyler asked me to ensure fluid level was correct. So had the transmission level verified and asked them to flash TCM with fast learn set up. I was only having trouble with the 5-4-3 downshift above 35 mph. Since the fast learn it’s definitely better on the 5-4-3 downshift. So far, rough out of the gate but finally working in….8,000 miles later though!

 

[R467X]

I received mine back in early December 2025 and had the NG VB installed by a transmission shop I use. There was a paper in the box that said DO NOT FLASH TCM (or something like that) let VB adaptive relearn new shift points. So I did that. A little rough at first but noticed each day it got better. I have about 8,000 miles on my NG VB with a couple to long haul toe runs with my Airstream. I took to a diesel custom guy here as Tyler asked me to ensure fluid level was correct. So had the transmission level verified and asked them to flash TCM with fast learn set up. I was only having trouble with the 5-4-3 downshift above 35 mph. Since the fast learn it’s definitely better on the 5-4-3 downshift. So far, rough out of the gate but finally working in….8,000 miles later though!

Can you clarify what "a little rough at first" means? Was there a violent jolt? Any check engine lights?

 

[Master Chief BT]

Can you clarify what "a little rough at first" means? Was there a violent jolt? Any check engine lights?

So there was some “violent jolts” on the way home from the install. I was told to expect some “hard shifts” up and down the 10 speeds. After a day or two those hard shifts got much better. Keep in mind I followed the directions in the box the VB came in that said NO TCM Relearn just the adaptive learn. I did not get any CEL or any codes. Still have not received any CEL or codes in my Banks IDash Pro. As I progressed thru the 500-1000 mile adaptive relearn initially some of the now I will call them “firm shifts” were still pretty constant in the 8-9-10 up shift and the 5-4-3 downshift. I was working with Tyler at NG and he told me to get fluid level verified and continue the adaptive relearn since I wasn’t getting any codes or transmission temps normal or even lower than what I knew as normal. So the firm upshifts resolved on their own and now the issue was just the 5-4-3 downshift. I was having a Ready Lift Level Kit installed at local diesel custom shop and I told him my 5-4-3 downshift concern and he said I should do a “Service Fast Relearn” on the TCM. He verified my tranny fluid level and said I was 1/2 quart low and he initiated the Service Fast Relearn. So far my 5-4-3 downshift has gotten much better and this now seems to be resolving itself after about 500 miles on this Service Fast Relearn. During this whole 8,000 miles on my NG VB to date I’ve never received a single CEL or code throw. Hope that added some clarity.

 

[R467X]

So there was some “violent jolts” on the way home from the install. I was told to expect some “hard shifts” up and down the 10 speeds. After a day or two those hard shifts got much better. Keep in mind I followed the directions in the box the VB came in that said NO TCM Relearn just the adaptive learn. I did not get any CEL or any codes. Still have not received any CEL or codes in my Banks IDash Pro. As I progressed thru the 500-1000 mile adaptive relearn initially some of the now I will call them “firm shifts” were still pretty constant in the 8-9-10 up shift and the 5-4-3 downshift. I was working with Tyler at NG and he told me to get fluid level verified and continue the adaptive relearn since I wasn’t getting any codes or transmission temps normal or even lower than what I knew as normal. So the firm upshifts resolved on their own and now the issue was just the 5-4-3 downshift. I was having a Ready Lift Level Kit installed at local diesel custom shop and I told him my 5-4-3 downshift concern and he said I should do a “Service Fast Relearn” on the TCM. He verified my tranny fluid level and said I was 1/2 quart low and he initiated the Service Fast Relearn. So far my 5-4-3 downshift has gotten much better and this now seems to be resolving itself after about 500 miles on this Service Fast Relearn. During this whole 8,000 miles on my NG VB to date I’ve never received a single CEL or code throw. Hope that added some clarity.

Thank you for that clarification.

I believe the reason you were 1/2 qt low is probably because the transmission shop you used followed GM fill procedure which is power brake to 170. As you know, transmission fluid expands and the hotter it is the higher the level will be. Where as next gen says to drive it until you reach operating temps, then come back and check the fluid level again. I believe in your case, as my case, operating temp is going to sit at 140 roughly.

This one's on GM with the stupidest design. It made replacing the up pipes easier but that's the only plus about not having a damn dipstick.

My plan to get this done today rained out.