The Titans announced the move Saturday.
Gray was hired by Texas, his alma mater, to be defensive backs coach and assistant head coach to Mack Brown last month.
Gray flew into Nashville on Friday to interview for the job. He spent last season as secondary coach at Seattle.
He replaces Chuck Cecil, who was fired in January a week before the Titans parted with head coach Jeff Fisher.
This is Munchak's second hiring since taking over on Monday.