The financially pressed Metro system is preparing to begin negotiations with the Washington area's largest transit union over a new labor contract against an unusual backdrop: some low-key cordiality.

After years of strained labor relations, the transit authority has taken steps to reduce friction with its employes' unions. Both Metro and union officials say they hope the lessened hostility will pay off in the upcoming talks.

"We have a goal," said George F. Babic, the transit agency's labor relations director. "We don't want the authority and the union to be at each other's throats. We realize that there's got to be a working together."

"At other times I've been critical of labor relations at the authority," said James M. (Tommy) Thomas, president of Local 689 of the Amalgamated Transit Union, which represents 5,600 bus drivers, subway operators, mechanics and other Metro employes.

"I can see almost 100 percent improvement. We still have problems, but we're solving more of those problems," Thomas said, quickly adding: "That doesn't mean that things couldn't blow up pretty soon."

For the Washington area, the impending negotiations may have a sizable impact. The bus and subway system runs up a deficit of more than $200 million a year -- a loss subsidized by local governments from real estate and other tax revenues. More than 50 percent of Metro's operating costs pay for labor.

Although strikes by Metro employes are prohibited, wildcat protests have occurred, including a seven-day walkout that crippled bus and subway service in 1978.

No strike has been threatened this year, but the issue has been raised by one candidate in a transit union election scheduled for next week.

The negotiations also may prove crucial for the union. Amid signs of fiscal austerity by Metro and local governments, the union is pressing for increased wages and benefits. It also is seeking to protect its members' jobs against inroads by nonunion county and city bus systems.

Local 689 is expected to hold preliminary talks with Metro shortly before Christmas, with full-scale negotiations set for early next year. The current three-year contract expires April 30.

The recent improvements in labor relations have been attributed largely to moves by Babic and his boss, Metro General Manager Carmen E. Turner. Babic was hired last year as part of a reorganization of Metro's much-criticized labor relations office, becoming the authority's fourth labor chief in six years.

Turner, who previously had cited "the instability" in Metro's labor office as a key factor in friction with the unions, said the realignment would focus "priority attention" on improving labor relations.

Since then, Metro has settled several key disputes with Local 689, including a protracted conflict over the agency's efforts to curb improper use of drugs and alcohol by bus drivers and other employes.

To defuse the issue, Local 689 and Metro officials agreed to set up a counseling program for employes facing disciplinary action for drug and alcohol abuse. Since the project's start last January, more than 200 employes have signed up to avoid being fired and almost 50 others enrolled voluntarily.

This fall, Metro and union officials ended another longstanding quarrel by revamping rules governing tardiness and absenteeism, a key issue for an agency that has to keep buses and trains on schedule. Officials said the revisions simplified a complex point system that repeatedly had triggered arguments.

One sign of the improved climate in labor relations has been a sharp drop in the number of disputes submitted to arbitration. The total fell from 91 arbitration proceedings in fiscal 1984 to 43 in the fiscal year that ended June 30. Officials said more grievances now are settled by lower-level supervisors.

Other union leaders also point to smoother labor relations at Metro. "With Babic coming on the scene, at least he's a professional," said Jim Sheridan, president of Local 2 of the Office and Professional Employees International Union, which ended a six-year battle with Metro this year. Local 2, the second-largest union at Metro, represents about 500 white-collar employes.

Some Metro officials trace the turnabout in labor relations to the last contract settlement with Local 689. The 1983 accord, which included major changes in cost-of-living and pension provisions, was the first in nine years to be reached through negotiations without calling in outside arbitrators.

Now Metro and union officials say they hope to avoid arbitration in the upcoming contract proceedings. "It's a good time to negotiate," said Thomas, contending that recent decreases in inflation have eased economic pressures. The union would have "egg on our face" if it invoked arbitration, he added.

In the negotiations, the union is planning to push for higher wages, an increase in Metro's share of health insurance costs and a reduction in the number of years required to qualify for retirement benefits. Bus drivers and subway operators now are paid $13.66 an hour after three years.

The authority is expected to try to hold down wages and cut costs by modifying provisions, such as those dealing with part-time drivers, meal breaks and preparatory time. A recent Metro report said the agency could save $2.9 million a year through "minor adjustments" in these and other contract terms.

Because of reduced inflation, the union's cost-of-living clause, once considered a key provision, no longer appears to be a volatile issue. Cost-of-living benefits were sharply curtailed in the current contract, and the union views the clause mainly as a symbolic issue if inflation remains low.

Partly because of recent moves by Alexandria and Fairfax County to set up their own bus systems, the talks also are expected to raise the possibility of a lower wage rate for newly hired bus drivers in suburban areas. Such a plan might help preserve union jobs while reducing Metrobus costs.

In next week's union election, Thomas, a soft-spoken, politically savvy, former Metrobus driver, is considered the front-runner. "He should win in a walk," said one labor official. Thomas became the first black to head Local 689 three years ago and, officials said, he has solidified his backing since then.

Thomas' opponent for president is Mike Golash, an avowed communist and Progressive Labor Party member who was defeated in two previous union elections. Golash, a Metrobus driver, was fined for contempt of court and suspended for six months by Metro after the 1978 wildcat strike.

Golash has called for a tougher bargaining stance and contended that the union should have the right to strike. "Each year, we've seen a modest retreat in our contract negotiations," he said in an interview. "We ought to stop that." Thomas declined to comment on Golash's campaign.