Ford Motor Co. Chairman Philip Caldwell last week became the first chief executive officer of a U.S. automobile corporation to be inducted into the United Auto Workers union.

The unanimous honorary gesture by members of UAW Local 898, which represents 3,100 hourly employes at a major Ford parts plant here, came complete with union card and sweater.

The emotional event marked Caldwell's last day on the job as a Ford employe. His 31-year career with the company, capped by his service since March 1980 as chairman and chief executive officer, ended Thursday with his scheduled retirement.

The successor to Henry Ford II, Caldwell was embroiled in a battle to revive the company.

Although he says he never feared it would fail, the task of slashing costs, improving auto quality, restoring profits and holding Japanese competitors at bay was immense.

"It wasn't a good time to live in Detroit," he said Thursday.

Caldwell has been succeeded by Donald E. Petersen, who is moving up from the Ford presidency in the first orderly transition of power in the company's 82-year history.

Caldwell was invited to spend his last day on the job here at Ford's Rawsonville Plant by workers who credited him with saving their jobs during the nadir of the last domestic auto industry recession.

The plant, in operation since 1956, daily produces thousands of carburetors, alternators, master brake cylinders, electric motors and other parts.

But when U.S. auto sales plunged from 10.5 million units in 1979 to 8 million in 1982, Rawsonville became one of many auto plants within and outside the Ford empire to be slated for closure.

But union and plant executives here put together a program to improve plant quality and labor-management relations.

They appealed to Ford officials residing in what is known colloquially as the "Glass House" -- Ford's world headquarters in nearby Dearborn.

Ford officials, at Caldwell's behest, gave Rawsonville a second chance. As a result, the plant today is regarded by auto executives and analysts as one of the best-managed, highest-quality facilities in the U.S. auto industry.

"It's been a rough five years. We all remember the layoffs. Every day, it seemed that this plant was going to close," said David A. Curson, a member of the UAW's National Ford Department who escorted Caldwell here for the farewell ceremony.

"But we didn't give up, and he didn't give up. Caldwell was in on every decision to save this plant," Curson said.

Caldwell angered many UAW workers and shocked some Reagan administration officials last year when Ford announced that he had received $7.3 million in pay, bonuses and stock options for 1983. U.S. Trade Representative William E. Brock, as well as UAW President Owen Bieber, called Caldwell's pay excessive.

But this day, the retiring chairman was brought here as a hero.

Workers cheered him as he traveled up and down aisles on a yellow electric cart.

And they cheered even louder when he urged them to continue along the path that saved the plant and helped turn around the U.S. auto industry.

"There are 380,000 employes of the Ford Motor Co. here and all over the world," Caldwell said. "This is the last day that I shall be one of them."

He said that there was no way he could thank everyone in the company for their support.

"But I can speak of what you have done here at Rawsonville, and I can also project you as a symbol and a part of what we have all done these past five long, long years," he said.

Caldwell said he would make only one final request of Ford workers, and that was to "take the fine example you have set and spread it . . . get even better."

He said "I won't be here to participate in it, but I won't be far away. I'll be watching."

Visibly surprised by the extension of honorary UAW membership, and wearing his blue pullover union sweater, Caldwell said:

"I wasn't really prepared for this. It wasn't in my notes. I don't even have a speech to throw away. I am proud, very proud. And when you say that it was the unanimous vote of the membership, I am overwhelmed."