Not sure if this is viable, but I wonder if you could try inducing vibrations in various places and see if it helps you narrow down the location. Like with a cheap massage gun you can find on amazon?
Edit: I meant inducing vibration from inside the cabin and trunk area, not a full substitute for driving over dragon's teeth lol.
https://www.amazon.com/s?k=massage+g...hl-bn-left_1_8