Private-party 2018 truck with 80k miles: test transmission and signs of crash repair

[Eric.B]

I'm going to look at a private-party used truck this weekend, a 2018 model with about 80,000 miles, and I want to be thorough but realistic about what I can check without a lift or professional tools. I know the basics like checking fluids and looking for rust, but I'm unsure how to effectively test transmission shifts on a short test drive or spot signs of past accident repair as an amateur. For those who've bought used vehicles privately, what specific items on your inspection checklist have saved you from a bad purchase, and what are the most telling signs of hidden mechanical trouble I should prioritize?