You have to let her cry. My now 9 mo. did the exact same thing and it used to make me so crazy that by the time we got to where we were going we were BOTH crying! Here is what I did: I hooked one of her lamaze toys to the headrest, put a suction cup toy on the little window, hooked her pacifier to her bib, put a bunch of toys in the passenger seat and off we went. For a while, she really like it when I would hand her a toy from the front. She was old enough to grab them and liked that they came out of nowhere. She would play with it for a while and then when she started to cry again, she would get another one and so on. I would give her safe objects out of my purse, sunglasses, etc. and she LOVES keys so we made a play set for her. I would also, when safe, reach back and help her put her pacifier in. When nothing worked, I just let her cry. She had to learn how to keep herself entertained. It was so hard. But I found that when I would sit back with her she would be overstimulated and not go to sleep. Now, at 9 mo. she is a champ in the car. She laughs and talks. She still fusses as she is on her way to sleep, but it is nothing like it was. Good luck!