Gray died at his home in Atlantic Beach from complications from pancreatic cancer, said his son Ed Gray, of Lyme, N.H.
Just last month, Gray ended 32 years of silence about his role in the Watergate scandal, telling a television interviewer that he had reacted with "total shock, total disbelief" to the revelation that his former deputy, W. Mark Felt, was the secret Watergate source known as Deep Throat.
"He fooled me," said Gray. "It was like I was hit with a tremendous sledgehammer."
Nixon appointed Gray, a former Justice Department official and submarine commander, acting FBI director in May 1972 — just weeks before the Watergate break-in — after the death of J. Edgar Hoover. Gray was forced to step down in April 1973.
Critics alleged he tried to thwart the Watergate investigation — a charge he denied — even as Felt was secretly feeding information to Washington Post reporter Bob Woodward.
When Felt was unmasked as Woodward's source more than 30 years later, Gray said he believed the trusted deputy had been unhappy at being passed over for the top job and had talked to the Post in order to sabotage him.
"I think there was a sense of revenge in his heart, and a sense of dumping my candidacy, if you will," he told ABC.
Gray was never indicted for any Watergate-related misdeeds, but descriptions of him as a Nixon loyalist who helped thwart the investigation and as someone the White House thought could be pushed around dogged him in the years following the scandal. He vigorously disputed the depiction.
"He still will go down in history as somebody who took the bidding of the White House rather than following the law," Elizabeth Holtzman, a member of the House Judiciary Committee during the Watergate hearings, told CBS Radio News.