Ford 3000 diesel tractor cranks hard and gets hot on starter?

It cranks hard and makes a slight grinding noise. The battery posts and cables get warm while the cable connection on the solenoid and the ground on the face of the starter gets real hot.

Guesses - battery is going bad ; starter is going bad

Clean the battery terminals (both ends) to make sure the resistance isn't coming from lousy connections. If that doesn't work follow Happy Gramps suggestions - probably the starter binding up - batteries are really not likely to overheat the wires because they are going bad or are bad.

Sounds like you have bad connections to the battery and starter. Take the connections apart and shine them up. Corrosion is a high resistance connection.