Same issue here. I have a 2023 2500HD with 30k miles. Taking off from a stop light the truck shifted really hard and went into low power mode. Limped home and took it to the dealer, its a valve in the allison tranny that needs replacing. They don't have a clue when the part will be in. It's been since June 17th now that it broke down. They wouldn't give me a loaner, so i had to argue for a rental car. Well I have wheels to get around but the suburban doesn't have any hitch. I pull 5th wheels for work and my camper. Needless to say its messed up my whole summer because of no tow vehicle. They are saying it could be a year..? Pretty ridiculous they you pay all this money for a truck they can't even fix. Got the Covid excuse for part back order... IT'S A DAMN JOKE.
