Yes, you can name a son after his grandfather.

From the point of view of Jain dharma and tradition:

• There is no prohibition in Jain scriptures about giving a child the same name as a grandparent or any elder.
• In many Jain families, it is actually common and considered respectful and loving to name a child after a pious grandfather, grandmother, or other elder.
• What matters more in Jainism is:

- The meaning of the name (it should be good, virtuous, non-violent in sense). - The bhāv (intention) behind the naming – respect, gratitude, and inspiration from that person’s good qualities.

Both Digambar and Shwetambar traditions are the same here; there is no separate rule on this.

So, from a Jain perspective, naming a son after his grandfather is completely okay and can even be a beautiful way to remember and follow his good qualities.