The highest-ranking judge charged in the Greylord undercover probe of corruption in America's largest municipal court system was convicted today of taking hundreds of thousands of dollars in bribes to dismiss drunken driving cases and fix parking tickets over more than a decade.

Senior Cook County Circuit Court Judge Richard F. LeFevour was found guilty of all 59 counts of mail fraud, racketeering and income-tax violations lodged against him by a special federal prosecutor.

The jury deliberated seven hours over two days. LeFevour's eight-week trial ended Friday in U.S. District Court here. The prosecution contended that LeFevour amassed hundreds of thousands of dollars in cash payoffs. The jury rejected the defense contention that LeFevour's extra cash came from successful racetrack outings, gifts from his six sons, and money his artist wife earned from selling paintings.

LeFevour, 54, who did not testify in his own defense, became a judge in 1968 and was supervising judge in Traffic Court for almost a decade. He remains free on bond pending sentencing Aug. 27.

A tall, gray-haired man with a dour expression, LeFevour showed no emotion when the verdict was announced. He has been on paid leave from his $65,000-a-year post as presiding judge of the sprawling court system's largest administrative district.

LeFevour is the third judge convicted in the investigation, named Operation Greylord after the wigs worn in British courts. One other judge has been acquitted, one is expected to plead guilty to corruption charges, and one awaits trial.

Another 11 "lawyers, policemen and bagmen" have been found guilty of charges stemming from the Greylord probe, according to an assistant U.S. attorney. A total of 28 persons have been indicted in the operation.

In the three-year, Justice Department-FBI undercover probe, a young federal prosecutor posed as a corrupt lawyer, a downstate judge on special Chicago court duty taped conversations with colleagues on a tape recorder concealed in his cowboy boots, and a judge's private chamber was bugged to pick up incriminating statements.

Many details of payoffs and case-fixing came from several former Chicago policemen who worked in the Traffic Courts, became bagmen, and agreed to testify in return for light sentences.

Although LeFevour faces a maximum penalty of more than 300 years' imprisonment and heavy fines, the two judges convicted earlier received sentences of 15 and 10 years respectively. The acquitted judge was suspended for one month by a state judicial board for questionable actions.

Because of LeFevour's status as a senior judge, and the wide-ranging charges against him, his case was considered the centerpiece of the Greylord probe.

Led by Dan K. Webb, former U.S. attorney for northern Illinois, who headed the Greylord investigation, the prosecutors presented a mountain of financial data that showed that LeFevour had at least $143,000 in unexplained extra cash income in 1978-82.

Webb accused LeFevour of "a course of judicial corruption unequaled in the annals of corruption," saying the judge "sold and peddled justice like it was apples" during his 17 years on the bench.

The prosecution relied heavily on seamy testimony from former policeman James R. LeFevour, a cousin of the judge's, who told of arranging bribes for the judge and passing the payments in sealed envelopes during brief visits to his chambers.

Others testified that LeFevour accepted $1,000-a-month cash "dues" from a "hustler's club" of lawyers he permitted to solicit cases from unsuspecting defendants outside certain courtrooms, even though no lawyers were needed.

The government also alleged that after a local television news report of ticket-fixing in Traffic Court, LeFevour masterminded the destruction of thousands of court records that could have revealed his complicity.

Other evidence showed that LeFevour dismissed a case involving thousands of dollars in parking fines against a luxury car dealer, while accepting the dealer's gift of free use of an expensive car. LeFevour also solicited a $16,000 loan from the same dealer, which he has not repaid.

In all, LeFevour sought, or accepted, $51,800 in loans from two fellow judges, various lawyers and former Chicago Bears quarterback Sid Luckman, a member of professional football's Hall of Fame.

Most of the loans have not been repaid, and LeFevour failed to list $24,000 of them on state financial-disclosure forms.

In closing arguments, Webb told the jury that LeFevour sought to live as though he had a $200,000 annual income, although his judge's salary never topped $73,000. The judge's debts grew from about $50,000 in 1978 to nearly $175,000 in 1983. Webb said that this was because the Greylord probe had dried up the bribes.