Actually there is very simple answer. Once you settle into freeway mode, her mind is into relax mode. The last thing she wants to do is interrupt her mindset. Regardless of if she has announced it to you or not, once you are out on the road, she has turned off all responsibilities and finally is in vacation mode. (as opposed to packing/prep/work mode). Explain before the trip that is something that is really a big deal to you and that you would like her to plan to get up and do some listening once you settle into the freeway zone mode. This way she will mentally wait to change modes until she has looked for and fixed the rattles. I can't tune out squeaks and rattles either. They have to be dealt with. DW has just learned to except that, so she doesn't switch modes until everything is truly settled.