April 1, 1983

FROM the Ringling Brothers to the Felds, father and son, from the Fratellini clowns to the Flying Wallendas, the circus has always been a family business. Children are ''born into the circus.'' Generations of aerialists, gymnasts and lion tamers are swept into dynasties. The current edition of the Ringling Brothers and Barnum & Bailey Circus in residence at Madison Square Garden is, in at least this one respect, archetypal. It is a family of families: the Kovatchevis, Dukovis, Parvanovis, Bauers, Brauns, Antaleks and, of course, the Gebels. For many seasons, the hallmark of the Greatest Show on Earth has been Gunther Gebel-Williams, the death-defying animal trainer. This time he is accompanied by a gaggle of Gebels: his wife, daughter and 12-year-son, Mark Oliver Gebel.

With sales of its small cars languishing, the General Motors Corporation announced today that it was cutting its auto loan rate to 9.9 percent from 11.9 percent for consumers who purchase its compact and subcompact cars and light trucks. The Ford Motor Company quickly responded with a comparable program. The Chrysler Corporation, G.M.'s other major domestic competitor, is expected to follow G.M.'s lead in the next few days. The G.M. and Ford programs, covering loans of any term, are available beginning Friday on 1983 models delivered by May 31, when the program ends, or ordered by April 30.

A tentative contract agreement was reached today between N.J. Transit and a faction of the United Transportation Union that struck nine state-owned rail lines March 1. Another faction of the union that has honored the monthlong strike and refused to work walked out of negotiations moments before the settlement was announced. Despite the division, John P. Sheridan Jr., Transportation Commissioner of New Jersey, expressed hope that the striking faction would ratify the agreement at a meeting scheduled for Saturday morning and that trains for 70,000 commuters would be operating again by Monday morning. ''We think, in analyzing the whole situation, that our choice was to forge ahead and get the trains moving again,'' Mr. Sheridan said. ''We have no indication there will be a strike by the other union group. We will work all weekend, and we hope to have trains running by Monday.''

The problems in fabricating the metal space frame that will form the centerpiece of New York City's new Convention Center have been partly resolved, the president of the Convention Center Development Corporation said yesterday. The official, George Schoepfer, would not estimate the extra costs or the construction delays that the problems would cause. But he acknowledged that to complete the building, the corporation would need to make use of $24 million in interest expected from the $375 million in bonds it issued, bringing the final cost to at least $399 million. The corporation pays interest to its bondholders but also earns interest on the money it holds before it is spent.

News Analysis Last Christmas, President Reagan was feeling beleaguered by Democrats who were riding high after their November election victories. His programs were under wide attack, and he told aides he felt there was ''nobody out front'' making his case. ''I want to get out there and tell my side of the story,'' he declared. His speech on arms control in Beverly Hills today culminated an extraordinary personal effort over the last three weeks that stemmed from that frustration last December. Using the pulpit of the Presidency, Mr. Reagan has taken the political offensive and demonstrated his capacity to dominate the political arena on such issues as military spending and arms control, where his policies have been under fire. He has pushed the controversy over the Environmental Protection Agency out of the limelight.