Sex With Shifter — Knob

It sounds like you're referring to a piece of creative writing, likely fanfiction or an erotic short story, with the title

Based on the phrasing, this would probably be a niche, humorous, or absurdist piece where a person has a sexual encounter with a car’s gear shift knob — possibly as anthropomorphic fiction, parody, or fetish material (object sexuality/mechanophilia). Sex With Shifter Knob