NHTSA Complaint #11625329 — 2023 GMC SIERRA 2500

I was driving on the interstate and had just exited to refuel. As I was re-entering traffic, I accelerated to merge, and suddenly, as I was about to pull in, I felt and heard a massive metallic crash, like the entire transmission had dropped. The engine sounded abnormal, and immediately, the dashboard flashed a warning: 'Engine Power is Reduced.' The check engine light came on, and I got messages saying the transmission needed service and to schedule an appointment. I called my dealership and took it in as soon as possible. After they held the truck for a while, the service manager told me a critical part was on indefinite backorder with no fulfillment date. He handed back my keys, saying they'd reach out when it arrived. I asked if it was safe to drive, and he said yes. Later, driving from Illinois to California, my truck malfunctioned again. This time, in heavy, 12-lane traffic, the same loud crash threw me forward, almost slamming my face into the steering wheel. My wrists and shoulders hurt from bracing myself, and my right shoulder still aches. Again, I got the 'Engine Power Reduced' warning and transmission service notice. Each time, this has put me and those around me in severe danger.