Grapevine can get awfully windy and then it doesn't matter what you are towing your boat with. I would recommend 101. There are only two grades if you take Hwy 1 up the coast to 101 and they are not nearly as long as the Grapevine. In my Jeep it recommends staying out of overdrive at all times to keep from overheating and to help breaking. After I got my surge brakes fixed I could not believe the difference in braking. Have a great trip.