At highway mile-marker 35, west of Grantville, Ga., on Friday, it occurred to Sister Robin Connell that the round-trip bus trek from New Orleans to Washington represented an uncommon commitment.

It would work out to 54 hours and 2,224 miles, starting at 5 that morning and presumably ending sometime Sunday night, broken only by a few rest stops and several hours of marching or standing in 95-degree heat before getting right back on the bus again.

"Fifty-four hours on a bus," she joked with a few of the 40 other people on the chartered Trailways bus from the New Orleans area who were making the trip for the march. "We must be crazy. Don't you think we're crazy?"

By the time that Sister Robin and her friends finally were marching along Constitution Avenue yesterday they had endured a wasted trip to Atlanta for a convoy that never materialized, the sudden disappearance of the other New Orleans bus when it made a wrong turn near the Pentagon, and a long walk to the march site because the Metro was clogged.

Still, all who arrived were jubilant.

"I have a lump in my throat. I feel great," said Susan Hansen, a 37-year-old carpenter, as the crowd of blacks and whites around her broke into strains of "We Shall Overcome."

Some of the 41 had never before been outside Louisiana. Others were veteran supporters of the civil rights movement who had joined in the 1963 March on Washington.

They were working-class people, black and white, Vietnam veterans and nuns, rank-and-file union members, and common laborers, part of the "Louisiana Coalition" of labor, civil rights and religious groups who had labored since May to make the trip a reality.

"C'mon bus. Let me feel some big wheels rolling," prodded 50-year-old John Miller when he wasn't serenading the bus passengers with his "low-down blues" songs.

Miller had never been away from Louisiana before Friday and was one of 23 carpenters whose trip had been financed by the New Orleans local of the Carpenters' District Council. There is no evident bitterness in Miller, who made the trip to stress the need for blacks to participate more in labor unions.

But Gloria Firmin, the administrative assistant to the president of the local Southern Christian Leadership Conference branch and the coordinator for the trip, felt differently.

"America is still a racist country," she declared. "We still live under an economic system that says property is more important than the individual. The laws have changed, but has anything really changed in the way we deal with each other?"

Everyone on the bus spoke of New Orleans as a city in transition, where black voters are expected soon to outnumber white voters for the first time in the city's rich history.

As the bus wound past the heart of the Old South--places such as Biloxi, Mobile and Montgomery--memories of injustices were vivid in the minds of some of its passengers.

The memories were especially strong for Junius Boyer, a retired social worker.

"I remember the trolley cars here in my younger days, said Boyer, 55. "We had to sit behind screens that said 'blacks only.' When we were in our early teens, blacks and whites played together, but as we got older I was told to call them 'Mr.' and 'Mrs.' Sometimes they acted like they didn't even know me."

Others had made the trip to the 1963 march, like 68-year-old Catholic Raynel Arriatti, who spoke mainly of the positive changes he has seen in the intervening years.

"My faith teaches me all men are equal. At the time of the '63 march we were not all equal," Arriatti said. "Now, you look on this bus and see us all living together. We almost take it for granted now."

Vietnam veteran Ed Lampman, who spent the trip making sure that no one got lost during rest stops, said that memories of his tour of duty as an Air Force sergeant at the Danang air base led him to see a link between the "fundamental militarism" of President Reagan and its perceived effect on social programs.

"Just because of this march we won't end up with jobs, peace and freedom," Lampman said, "but we can bridge gaps that have historically existed between whites interested in disarmament, blacks in civil rights, and the labor movement."

After the day's events, the sweat-drenched group walked back to their bus in the North Pentagon parking lot. Sitting under the upended baggage doors of the bus to benefit from the shade, they rested, sipped water and described their feelings about the day.

Raynel Arriatti, badly sunburned, said: "Both my legs gave out, but I made it and I'm happy about it." He added that the trip was worth it, saying, "When I saw that crowd, I was just elated."

John Miller reflected: "I just wish some more people from home were here to hear it. The issue is justice. Peace and freedom without justice would be tough."

Henry Banks, a 26-year-old carpenter, declared: "I think everything was beautiful. Ronald Reagan is through. We showed him today he is out of it." Banks said that he especialy liked the speeches given by Benjamin Hooks, Andrew Young and Harry Belafonte.

"At one point," chimed in Susan Hansen, "I didn't realize how many people there were." She said that after she found a vantage point from which to get a better look, she appreciated the size of the crowd. "All of those people there together, it was a real high to recognize how many people shared my ideals."

The trip had started on a sour note, 50 minutes late because there were 82 available seats and about 100 people who wanted to go. A collective sense of gallows humor eased the problems. When the buses finally rolled off, the driver suddenly announced that they would have to change buses because of a leak in a grease seal.

"Sabotaged already," someone joked from the back of the bus.

Then, when the passengers had gathered up all their luggage again, the driver decided that the leak was not too bad and decided to drive the bus after all.

Observed 40-year-old carpenter Stanley Williams: "This is starting out like a Baptist church meeting: late."