My brother will be making this trip in a couple months with an overloaded Toyota towing at max capacity. I was hoping for a Google maps like solution that would allow him to select a maximum grade incline but so far no luck. On the bright side I did stumble across this forum which seems to have similar posts.
The "hills" of Tennessee will most likely be the worst section I'm guessing. He is okay with adding a decent chunk of time to avoid wrecking his transmission. Any input would be greatly appreciated.