F1® 2018 Easy way to get It's in there somewhere Trophy/Achievement Video Guide
Either 3 lap or 5 lap race so career or grand prix mode with full damage now race it normally until final lap (make manual save if you want) now if you was on auto gears change to manual, Now rapid change up and down gears until 70% close to finish line like i do in the video and hopefully you will get told you are now missing a gear now just finish the race that easy.
It's in there somewhere
Finish a race with a missing gear