He is the family’s initial patriarch. To understand how old he is the author even described that he and his wife sleep in the barn because they need to wake up very often during the night to use the bathroom.
This personage is the head of the family and, as you see, a very old man at the same time. Nevertheless, he is not the typical old man. He is full of energy, lustful and a little bit earthy. His character has got something from a child too. He is kind, but he likes shouting, sometimes he behaves even outrageously. Being an old man, he sometimes forgets to wear his pans after the bathroom.
At the beginning of the story, we see him as a person who is ready to begin his new life and to start living again in the new place with his big family. He keeps saying about crushing grapes and lets the juice running his face. Ironically, but it always happens with people, when it is time to depart we don’t want this happen. The same thing happens in the book. Pa Joad doesn’t want to leave a place where he was born, where he was growing up and living his entire life. He became very stubborn, mad and proud. What did his family do with it?
They decided to drug him as they understood it was the only way to move from this place with Grandpa, take him off of the property. Unfortunately, he was never again conscious after they all leave. After the first day of departure, when the whole family makes a camp, he accidentally gets a stroke and dies. His family buried him in the ground of the field. And it seems to be so sad that all his efforts to live better failed.
Grampa Joad in the Essays