2023 Allison transmission valve assembly

[DBD1979]

I am having the same issue now with my truck, shifting issue and going into power reduced mode. First time it happened I cleared it by disconnecting the batteries for some time. Second time I took it to the dealership, they flashed the computer and said they couldn't replicate the issue and to bring back if it happens again. Well last night it happened again, had the truck back for less than a week. Have not even used a full tank of fuel. I am dropping it back off today, I will update with outcome. Glad I seen this thread to see its an actual concern, I'm sorry for all those that are dealing with this. I paid 90K for a crap box, currently have 36.5K on the clock.

[Major Tom]

Text below is from NHTSA Check for Recalls web page:

 

 

"Oct 24,2024

Manufacturer Recall Number N242454440

NHTSA Recall Number 24V797

Recall Status Recall Incomplete, remedy not yet available

Summary General Motors has decided that a defect which relates to motor vehicle safety may exist in certain: 2020 – 2022 Chevrolet Silverado1500/2500/3500 and GMC Sierra 1500/2500/3500 and 2021 model year Cadillac Escalade and Escalade ESV, Chevrolet Suburban and Tahoe, and GMC Yukon and Yukon XL vehicles equipped with diesel engines. A transmission control valve in some of these vehicles may be susceptible to excess wear over time, resulting in a gradual loss of pressure within the valve that can cause harsh shifting. In rare cases, the rear wheels may experience a momentary lock up. If the rear wheels lock-up momentarily while driving, there is increased risk of a crash."

 

Yes, my truck is on the list.  Had some bad sensors replace on the truck last week and the dealer said they (GMC) did not currently have a fix!

[hksegers]

Same here, 2023 Silverado 2500 10 spd Allison 63k miles. Truck clunked real hard and now I’m waiting on a Valve Body replacement. Truck broke down in Minnesota and I live in Missouri and used it for my work truck. Never had a Silverado Duramax and was enjoying it for a solid 4 weeks till this happened. Haven’t even made the first payment and already stranded. 

[Rick_]

Has anybody installed a Nextgen VB kit or VB and remedied the issue? 

Since the kit is only $800 and is available, it seems it would be a viable alternative to letting trucks sit at dealerships for weeks or months hoping that they have engineered a a permanent fix.

My 3500HD trans is working fine at 30k miles but my 2022 1500 Baby Dmax 10spd might get a little preventative maintenance...

[LocoS1]

On 12/18/2024 at 10:58 AM, Rick_ said:

Has anybody installed a Nextgen VB kit or VB and remedied the issue? 

Since the kit is only $800 and is available, it seems it would be a viable alternative to letting trucks sit at dealerships for weeks or months hoping that they have engineered a a permanent fix.

My 3500HD trans is working fine at 30k miles but my 2022 1500 Baby Dmax 10spd might get a little preventative maintenance...

I've had many buddies who have had to go nextgen and solved the issues prior to the fab rats video being released. If you have seen it. 

 

[nparker76]

I had this same issue back in May. 2023 2500 with 21k miles. I was on a 31-day camping trip pulling a 5th wheel camper. I was only on day 4 of the trip and 1000 miles from home and the CEL and reduced power message came on. Dealership diagnosis was it needed a new valve body. Parts on nationwide backorder and any dealership that did have the part wouldn’t let it go because they had trucks lined up waiting on the same thing. I was forced to trade in the truck, or cancel our big vacation and figure out how to get my camper and fam back home. GM was no help. Like another post mentioned, they were still rolling out new trucks which means parts are available on the assembly line. But GM seems to prioritize new sales over keeping existing sales road worthy. I lost $27k in the deal in order to get back to a similar monthly payment due to a crappy trade in value and no discounts. GM gave me $500 in GM reward points and like $250 worth of on-star package extensions “for my inconvenience”. They could have offered new trucks which means rebates, loaner vehicle, or found the parts. It was a disappointment. I wrote a complaint letter the GM as well, but never received a response. I will likely swap away from GM on my next truck because of this crap, which generally happens every 2-3 years. My new 24 model gets worse mileage. I mean it’s a big diesel so I’m not expecting high mpg, but geez it gets lower and lower with every new design. That’s completely backwards on how it should be. I’m getting 13.5 mpg in my ‘24 where I was getting around 16 mpg in my ‘23…same route to work. And was getting even better in my 2018. Regens every 150-170 miles. It’s crap. Do better GM. 

[GLong]

Having the EXACT same issue with my 2023 AT4 3.0. with 30,000 miles.

The "transmission" specialist relayed it was #1 & #4 solenoids sticking..."common problem". The Service Manager relayed there were none available in the US, factory backordered. Apologetic added, I have no idea when we will get them could be 2 weeks, 2 months or 10 months. 

Is there a class action suit on lemon law protection? My fear is, they fix these then 2 more fault in 6mos and so on. 

I went with the diesel for long term use with limited issues. 

[vucelick]

The half-tons use a completely different 10 speed transmission than the HD trucks.  So looks like it covers both transmissions

Edited February 27, 2025 by vucelick

[Okanagan Jerry]

I have got the exact same issue @30 on my 3500

 

Dealer had diagnosed problem, ordered part but has idea when it will arrive? 

if this is a none issue a) Has Allison / GMC come up with a permanent fix ? b) I need my truck I have been given a small GMC suv loaner but it won’t pull my trailer.

 

Sounds to me like a faulty casting or ?

 

 

[Elite130]

I just had the valve body take a $hit on my 2022 Silverado 2500. I just turned over 40k miles. No warning at all. I was pulling out of a shopping center parking lot onto a main road and as I was accelerating, the truck hesitated and jerked about 4 times. Then the truck lost all power and then got a check engine light and reduced engine power warning on the DIC. I pulled over at the next shopping center. Put the truck in park. Ran codes on my iDash and got a P0700 "lost communication with transmission BCM" code. I didn't reset the codes. Turned the truck off for about 15 min and restarted it. Put it in gear and started driving again. The transmission was stuck in 5th gear. I could drive the truck normally (still in reduced power mode). My house was 3 miles away, so I limped it home so I could get all my work gear out of it knowing I would be without my pickup for weeks. An hour goes by, I get back in and proceed to drive it to the dealership. Truck is shifting normally, but still in reduced power mode.

 

Diagnosis - Bad valve body, transmission fluid appeared to be burned with signs of metal flakes. New VB is on order and full rebuild may be necessary. All work covered under warranty. 

 

The item I do not understand is the burnt transmission fluid. I watch my tranny temps when I haul all the time. Never have I gotten the tranny temp hot nor did I ever receive warnings. Thoughts?

[TripleBGM]

Concerning.....