In the olden days, 4x4 meant 4 on the floor and 4 wheel drive, but just about everyone is now using automatic transmissions.

In the '08 Super Duty brochure, they refer to a "F250 FX4 Crew Cab 4x4 in Black..." and it says that "4x4 drivetrain with limited-slip rear axle" is standard with the FX4 package.