Jim 2022

I agree, this forum was so helpful in identifying the issue, even though the mechanics wouldn’t take my word for it in the beginning and took several days to finally replicate the problem. Kudos to my dealership though for providing me with a rental car throughout the whole ordeal and never having to pay a dime upfront. Best of luck!

Update...the dealership received the replacement valve body for my new 2022 GMC Sierra 2500HD Denali. They got it installed and I picked up my truck on 12/1/22 and have not had any more problems so far. The highest temperature that I've seen the transmission fluid reach so far is around 155 degrees. I have yet to tow anything but the temperature was reaching around 256 degrees before and without towing anything. Yay!

Update...I just called again to check the status of the valve body part that has been on back order for my truck. My truck has been parked at the GMC dealership service department since 10/13/2022. I finally have an ETA date of 11/30/2022 for the part to arrive. Hopefully the part will arrive at the end of the month and that it will resolve the issue! I'll provide another update the first part of December.

That's awesome news! I'm still waiting on the valve body to arrive and hope to have my truck back soon! Thanks again for posting and sharing.

Update: I dropped off my brand new 2022 GMC 2500HD Denali on 10/13/22 for the tech to determine why the transmission was overheating and going into 'limp' mode. It took about a week for them to diagnose the problem and said it is the valve body. Today is 11/1/2022 and my truck is still in the shop waiting on parts. No ETA on the parts as of yet. I will provide another update in a week or two. Stay tuned!

Thank you so much! I spoke to the service department and provided them with this bulletin number. They indicated that the bulletin states to check for a twisted cooler line and to untwist it, if it is found to be twisted? I have an appointment on Thursday so I'll provide an update later. Thanks again!

Hi there. Do you by chance happen to know the GM Bulletin number or have a copy of it? I have an appointment at my GMC dealership on 10/13/22 and they are not aware of this issue or the bulletin. Thanks!

Thank you. I just emailed you the information that you requested. I do have an appointment scheduled for October 13th to have the dealership look at my truck.

Hi there, I'm new to this forum and joined to see if anyone else was having similar issues that I am. I just purchased a 2022 GMC Sierra 2500HD Denali and immediately had problems with the transmission overheating and automatically downshifting to low gear. With only 200 miles on my truck and not towing, my truck starting down shifting into low gear while simply cruising around 35-45mph. The transmission oil warning light displayed and I could not get the truck to go into any other gear but low. I immediately pulled over and put the truck in Park and waited until the transmission cooled down. Even after the transmission had cooled, I could only get the transmission into something like Low 5 the remaining 3 miles to home. Only after shutting off the truck and letting it set for 5+ hours did it start shifting and running normal. I used the truck for another 1000 miles with no problems, until yesterday. The same thing happened again after a leisure drive and not towing. It started downshifting into low gear as if I were towing a load uphill? The transmission warning light did not come on but I had to put it in Park and wait for at least 30 minutes before it began shifting normal again. I noticed this morning that the transmission reached 219 while on just a short drive, which I'm not sure what the normal temperature should be? I'm hesitant to even consider towing a 5th wheel after these two experiences.