Gallaudet College President W. Lloyd Johns resigned abruptly yesterday after only three months in the job and after the board of trustees' refusal last week to endorse his continued leadership.

Johns announced his decision to quit in a letter sent to a closed-door session of the college's board of trustees. He did not attend the meeting and could not be reached for comment. The letter gave no reason for his resignation.

Stability has been a hallmark in the history of the world's only liberal arts college for the deaf. In its 118 years, Gallaudet has had only four other presidents. Until yesterday, the shortest tenure of a Gallaudet president was 14 years and Johns' sudden resignation sent shock waves around the country.

"It caught many of us by surprise," said Jack Gannon, director of the office of alumni and public relations and a Gallaudet graduate who spoke through an interpreter. "For the three months he was president he developed a good relationship with many of the people on Kendall Green," Gallaudet's campus.

Chuck McFadden, a spokesman for California State University at Sacramento, where Johns was president before coming to Gallaudet, said he "left here with all flags flying."

Johns' letter of resignation, effective immediately, said only that "My tenure as its chief executive officer will never be forgotten . . . I wish Gallaudet well in the years ahead. . . ."

According to Gallaudet officials, Johns met with the full board last week and told them that he would not feel comfortable staying on at Gallaudet unless the board gave him a letter endorsing him and expressing full support of his management style.

"We felt we could not do so," said Jane Spilman, chairman of Gallaudet's board of trustees. But Spilman gave no specific reasons for their decision. "It is a gray area. Certain things bothered some board members.

"Sometimes in human relationships both parties realize it is a poor match," Spilman said, "not that there is any controversy but that there is a poor match . . . we feel very comfortable" with Johns' decision to resign.

Part of the reason for his departure, some Gallaudet officials suggested, lies in the college's special status, described by Spilman as "a beacon for the hearing impaired."

One college official said the college's status may have placed extraordinary demands not only on the college president, but also on the president's wife. Johns' predecessor, Edward C. Merrill Jr., and his wife Frances were "very active in the college," said the official, who asked not to be named.

Merrill was described by Gallaudet officials and staff as a courtly host to Gallaudet's many visitors from around the world and as a tireless president who even changed light bulbs around campus and pulled weeds in its gardens.

"This is my opinion. Johns had very big plans for Gallaudet," Gannon said, such as reorganizing the administration and putting a tight lid on spending. "Then he realized the complexity of the situation and that may have slowed him down a bit," said Gannon.

Spilman said a search committee was set up yesterday to find a new president and will begin work early next month. Gallaudet's vice president for business and administration, Jerry Lee, has been named interim president.