Transmission

It sounds like the transmission is low on fluid. I would check the fluid and then service the unit.

Here are some guides and diagrams to help you get the job done:

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

Below are some diagrams for your car.

Transmission fluid level should be checked monthly under normal operation. If the vehicle is used for trailer towing or similar heavy load hauling, check fluid level and condition weekly. Fluid level is checked with the engine running at curb idle speed, the transmission in neutral and the transmission fluid at normal operating temperature.

Please let us know what happens.

Cheers, Ken

I checked the fluid, it’s full and looks clean

Can you shoot a quick video of what the truck is doing and then upload it, I cant tell if it is a tranmission things are an engine issue?