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Transmission won't upshift if it goes into 2nd gear unless 4000rpm's

I have a 2016 GMC Canyon diesel. I love the truck except for one item. When going down a hill the truck downshifts, as it should. I have a particular hill near my home with a sharp turn at the bottom. The truck will shift all the way into 2nd gear. When I hit the gas at the bottom the truck will not shift up until the rpm’s hit about 4000. I had the dealer send a guy with me and he told me this isn’t right but could not find a reason. I was in contact with GMC and asked them to have a representative go with me on a drive when they were in the area. They agreed. Then after a few months of telling me they were working on it, they contacted me and said they weren’t going to do it. They said work with my dealer. My dealer says there is nothing they can see to fix although they agree it isn’t right. Anyone else having this issue and can anyone give me advice on what I can do?

I can’t offer any more advice other than to check your state’s Lemon Laws to find out what it takes to have GM buy this truck back, assuming they can’t fix it.

And since they see no issues, anything they do is a bit of a guess.

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Can you get this in writing? If so, send that to GM HQ.

The shifting decision is based on hydraulic fluid pressures and electrical solenoids. And vehicle speed. Those should be all testable and repairable, although in some cases the only economical repair might mean a new transmission. I don’t understand why they say there is nothing that they can see to fix. Ask them if they’ve tested the hydraulic fluid port pressures and verified the solenoids are all working. And that the vehicle speed sensor is accurate. And ask the dealership to have one of their tech staff go along with you in a ride in one of their new GMC Canyons they have on the lot to see if the new one does the same thing or not.

I’m a little bit disappointed with the dealership’s attitude

They say the transmission’s not operating as it should

Yet they also say they intend to do nothing about it

Seems to me if they say somethings’ not right . . and the truck should still be under warranty . . . then they’ve got some work to do, at no expense to the customer