Not heating up
 

My dad has a 2001 7.3. He bought it brand new and has never done everything to it besides basic maintenance. Anyways i was driving it home for him one day it the temp needle never got higher then the bottom line. I drove it on the freeway going over 60mph for about 30min. I am very familiar with 7.3 i currently own an 02 and had a 99. Could this be just a bad thermostat? I have never ran into this problem before. Also it wont go out of overdrive.

Sounds like the thermostats to me