The National Highway Traffic Safety Administration is feeling growing pressure from consumer advocates to take action against the Ford Motor Co. for an alleged flaw in nine million Ford automatic transmissions that could cause them to pop unexpectedly from park into reverse.

Although the case dates to July 1977, when the Center for Auto Safety, a Washington-based consumer group, petitioned NHTSA to investigate several reports of park-to-reverse incidents, the government probe has been a case study in frustration.

On more than one occasion, NHTSA has been "within days" of issuing what would be one of the largest auto recalls in history, involving nearly 9 million 1970-78 Ford vehicles with the automatic transmissions in question.

But each time there was a last-minute setback. The most frustrating delays were caused by two crucial statistical reports that were compiled by outside contractors and found to be faulty.

And government researchers have failed to find an "absolute mechanical problem" with the transmissions, NHTSA sources say.

NHTSA has received 10,000 complaints about the transmission problem, far more than those received about transmissions from other cars. And the agency is investigating unconfirmed reports of as many as 60 deaths, 1,100 injuries and 3,700 accidents traced to the Ford park-to-reverse problems.

The frustration of the NHTSA was furthered earlier this week when a Fairfax County Circuit Court jury awarded a Falls Church woman $50,000 in suit she filed alleging that one of the transmissions caused her injury.

In what was the park jury finding against Ford in a park-to-reverse transmissions case, the jury apparently agreed with the woman's contention that a motorist could believe that the transmission was in park when, in fact, it was not.

The woman, Constance Bartholomew, had been loading groceries into her 1973 Lincoln Continental when it suddenly went into reverse, struck her and hit some nearby parked cars before stopping.

It has been Ford's contention all along that there is no problem with the transmission. The company has maintained that any problems are caused by consumer misuse of the transmission and failure of motorists to use the parking brake when the car is in park.

The reason for the extraordinary number of complaints about Ford tranmissions, the company says, is the widespread publicity the problem has received.

The Center for Auto Safety is pressing on, however. Center director Clarence Ditlow said the government doesn't need to show the specific design defect in order to mandate a recall. All it has to show is widespread consumer failure.

But NHTSA's Joan Claybrook has been particularly careful on this case. The number of cars involved in the recall ensure that Ford will appeal any order, and if NHTSA doesn't have an ironclad case showing a design defect, agency officials fear that it could lose a court battle that could set bad precedents for future actions.

"We just don't have a broken part, or anything that doesn't work right," says an agency source. "And we don't have a state-of-the-art for the industry that shows Ford to have made a mistake, or to have failed to use the best technology."

"We're terribly concerned about this investigation," Claybrook said in an interview. "And we're diligently trying to analyze different parts of the issue."

But she would not promise any time-table for action on the 2 1/2-year-old investigation.

"All I can say is that it would probably be helpful to tell motorists that many of the injuries reported in this case occurred because people chased after their cars," she warned.

Sen. Wendell Ford (D-Ky.) didn't make any friends in the consumer movement when he led the charge against the Federal Trade Commission in the Senate Commerce Committee last week.

After his proposals to curb FTC powers were introduced, Ford found himself in the embarrassing position of being the proposed recipient of the National Consumer League award for consumer leadership.

So he dropped a not to NCL's executive vice president, Sandra Willett, askingher to reconsider.

Which she did. He won't receive the awards.