In looking at the route I might take I discovered Darien Gap – Impassable jungle between Panama and Columbia. Do they have a ferry?

Here’s a link to an attempt to cross it in 1975.

I also remembered reading a book about two guys driving the whole thing in a truck. Tierra Del Fuego to Prudhoe Bay. I think it was by Tim Cahill. I’ll have to look into that.

More to keep in mind:

Make sure your paperwork is in order and there are no ambiguities; ie, on your vehicle insurance papers, make sure the VIN and plate numbers match exactly. Make sure nothing has expired or will expire during your trip, and that you have at least two copies of everything, kept in separate locations. I never let people wander off with my passport – if they need to show it to someone else, they can take a copy or bring that person to the passport, which doesn’t leave my sight. Have the phone numbers and addresses for embassies in each country you’ll be visiting. Make sure you always have water on you, and containers for more. Make sure you don’t run too low on gas, and have containers to get more should you run out. If you have the money, you could take a sat phone.