Around 76k miles, a whining occurs upon accelerating. Hear ever so slightly in 1st gear. Gradually is more evident as the speed increases. At 78k I decided it was definitely getting louder and was concerned after researching and learning that MULTIPLE 2021 Highlanders have needed transmissions replaced. I brought it in to a mechanic who searched for every possible problem, but ultimately came back to tell me it is my transmission failing.