D.C. Superior Court Judge Robert H. Campbell, who is under investigation by both a federal grand jury and the city's judicial tenure commission, is seeking to retire because of medical disabilities, a lawyer for Campbell confirmed yesterday.

Harry S. Wender, who said he represents Campbell with attorney Jacob A. Stein, said yesterday that Campbell's application for disability retirement, supported by medical certification of the judge's physical illness, is pending before Mayor Walter E. Washington. Washington leaves office on Jan. 2.

There was indications yesterday from various sources that Campbell's request for medical retirement would be granted in the last days of the Washington administration rather than after Mayor-elect Marion Barry takes office on Tuesday.

The Washington Post disclosed in July that a federal grand jury here was investigating allegations of favoritism in Campbell's handling of hundreds of overweight truck violations issued to Excavation Construction Inc. The stories also said that company officials had been called to testify before the grand jury and that firm records had been subpoenaed.

The grand jury investigation followed a four-month FBI investigation, sources said at the time.

Last April, The Post reported that the D.C. Commission on Judicial Disabilities and Tenure was investigating allegations of judicial misconduct by Campbell in his handling of large numbers of tickets in the city's traffic court. Sources said then that the commission's investigation also concerned masses of tickets issued to firms with large fleets of vehicles.

A spokesman for the mayor's office said Washington was out of town on personal business and could not be reached for comment.The spokesman also said that he could find no record in the mayor's office of Campbell's application for medical retirement.

Wender refused to comment on his client's physical condition except to say "there are a variety of illnesses. So far as I know, they are all permanent."

Campbell, 56, has been absent from the Superior Court for the last two to three months. Various sources have said that Campbell, a judge since 1972, is blind in one eye and has impaired vision in the other. In addition, it was understood that Campbell was hospitalized this fall for a serious throat infection.

At least one of Campbell's lawyers recently met with officials in the U.S. attorney's office here and discussed Campbell's retirement from the court for medical reasons, it was also learned yesterday.

The tenure commission has the power to remove, publicly reprimand or otherwise discipline a judge of the local court. Some sources indicated yesterday that if Campbell were to permanently retire from the Superior Court, the tenure commission's investigation would be brought to a close. His retirement, however, would apparently have no effect on the criminal investigation, these sources said.

Under District law, a judge who has been on the bench for five or more years may voluntarily retire because of a physical disability that is permanent or is likely to become permanent and that prevents or impairs the judge's performance of his or her duties.

In order to establish such a disability the judge must supply the mayor with a certification of illness, signed by a licensed physician, according to legal requirements. The mayor then determines if the disability warrants a medical retirement and subsequent pension benefits.

Percy Battle, a retirement system specialist with the city government, said yesterday that Campbell would be eligible to receive a minimum of 50 percent and a maximum of 80 yercent of his current judge's salary of $49,050 if he were granted a medical retirement. The actual amount would be computed on th basis of Campbell's length of service with the city government, Battle said.

Battle and other city officials said yesterday that such pension benefits are taxable.

Campbell could not be reached for comment yesterday on his request for a medical retirement. In connection with the investigations, he has earlier denied any improprieties during his service in the local traffic court.

Campbell joined the D.C. corporation counsel's office in 1954 as an assistant city prosecutor and was named assistant chief of the law enforcement division in 1963. He became chief of that division in 1967. Five years later he was appointed to a 15-year term on the Superior Court bench by then-president Nixon.

During his tenure as a judge, Campbell has been criticized by some lawyers, who contended he handed out tough penalties to individual defendants who appeared in traffic court but was lenient with some large corporations.