I have a 2023 gmc AT4 w/ 3.0L diesel. Had several weird shifts over the 40,000 miles I have on it. First time in shop they said it was the DEF system, within a week the transmission shifting became much worse. Engine light came on and truck went into “limp mode”. Feels like it’s in 3 or 4th gear all the time, will not shift. I can for about 50mph max before my rpm’s get too high for comfort. Plus take off is slow because it has no torque.
GM Dealer says same thing - Bad Valve Body in the tranny.
national back order, said could take several months and has no idea when it might arrive. After reading blogs (THANK YOU ALL) I’m going to see if entire tranny can be authorized and will call GM if needed. This is crazy for a truck that cost over 70k!
if that doesn’t work will trade for Tundra…
