You are already capable of communicating to your cat that you are in pain. Be honest. Make sounds of pain when they hurt you, the same way you would train a kitten not to bite or claw with malice. Your cat will understand. Just don’t get angry. It’s easy for cats to forget about empathy in the face of anger.
Either way, you can put passengers in the back of an SUV, but not in the bed of a truck (without breaking laws or being totally unsafe).