The Senate voted yesterday to split the Deep South's 5th U.S. Circuit Court of Appeals in two. A few years ago that would have set off a major civil rights fight. Yesterday there wasn't a ripple of opposition in the Senate, though there was some grumbling by civil rights leaders outside.

The 5th Circuit, which includes Georgia and all the Gulf states from Florida to Texas, is where many of the landmark civil rights cases of the 1950s and 1960s began. It produced a group of strongly pro-civil-rights judges.

It is a huge circuit in both caseload and geographical size, and judicial commissions have been recommending that it be split for years. But the proposal acquired an "Eastland history" and was opposed by civil rights groups; when former Judiciary Committee chairman James O. Eastland (D-Miss.) tried to split the circuit, it was widely perceived as an effort to move Mississippi into a circuit that wouldn't enforce civil rights too strongly.

His effort to attach his plan to a bill creating nearly 150 new federal judgeships held up that legislation for months four years ago, but he finally gave up in the face of House opposition.

Last week, Sen. Howell Heflin (D-Ala.) joined by all senators from 5th Circuit states and the new Judiciary Committee chairman, Edward M. Kennedy (D-Mass.), introduced the new bill to split the circuit. One part would include Texas, Louisiana and Mississippi; the other, Alabama, Florida and Georgia. The bill was not referred to committee but put directly on the Senate calendar. Yesterday it was passed by a voice vote without opposition.

Heflin told the Senate the civil rights fight has gone out of the issue and that all 24 judges on the circuit court, including its first black judge, favored the move, the better to handle the work load. He said that the NAACP and the Lawyers Committee for Civil Rights support splitting the district. A Heflin spokesman said the two new circuits would be ideologically identical with the present circuit on civil rights.

But Joseph Rauh, a Washington lawyer and a leading member of the civil rights movement for years, said the NAACP and Lawyers Committee still oppose splitting the circuit.

Rep. Don Edwards (D-Calif.), chairman of the House civil rights subcommittee, said he thought it probably true that the split is not much of a civil rights issue any more. Most of the major court battles have been won. But it may face House opposition, on grounds that reforming the circuits should not be handled on such an ad hoc basis but as part of a nationwide change. The 9th Circuit on the West Coast is bigger than the 5th.