Ford Motor Co. directors voted yesterday to slash the troubled auto manufacturer's quarterly dividend rate, an action widely anticipated by Wall Street analysts in recent months.

The Ford action came as, separately, there were these other industry developments:

Maryland and Baltimore officials, as well as union spokesmen, told the Baltimore Sun that General Motors Corp. plans to renovate and expand its 45-year-old Broening Highway factory, which employs 6,000 workers. The renovation reportedly will include a new factory building, and GmY won't close the plant, as feared earlier by c ity economic officials.

Detroit figures showed that U.S. automakers will assemble 35 percent fewer cars this week than a year ago. The five U.S. firms plan to make 101,950 cars, up slightly from 101,411 last week, said Automotive News.

Ford, in the biggest dividend cut in its history as a publicly traded company, reduced the payout to 30 cents a share from $1.00, starting with a distribution on Sept. 2 to owners of record Aug. 1.

Ford Chairman Philip Caldwell well described the payout reduction as among "prudent steps" to improve Ford's financial condition. Earlier, Ford trimmed annual operating costs by $1.5 billion, cutting payrolls and closing some plants. Ford also outlined a program to cut overall spending by $1.5 billion between now and 1984 as part of a strategy of conserving cash to apply to development and introduction of new, fuel-efficient cars here and overseas, where Ford remains a profitable business.

Industry analysts had expected the cut and were surprised when Ford did not do it at the second-quarter dividend meeting three months ago. Some thought the dividend would be eliminated entirely. Ford lost a record $164 million in the first quarter.

According to estimates of Wall Street analysts, the No. 2 automaker could report a $350 million loss in the second quarter and more than $1 billion for 1980 overall, all because of much steeper North American losses that exceed profit from non-auto and foreign subsidiaries.

Yesterday's action saves Ford $84.4 million a quarter, or $338 million a year.

That still leaves Ford with about $4 billion a year in investment programmed through 1984. The company borrowed $400 million in the bond market this spring and arranged short-term loans from its German and British subsidiaries totaling $1 billion last December.