Henry Ford 2d, who took over the ailing auto company founded by his grandfather and restored it as one of the world's industrial giants, died in Detroit of complications arising from pneumonia. He was 70 years old. Mr. Ford fell ill while visiting Germany in August and returned to the Detroit area on Sept. 5 1987. He had been in intensive care in the hospital named for his grandfather, Henry Ford, since Sept 14 1987. World War II had just ended when Mr. Ford, backed by his mother and a few allies, seized control of the company. By then his grandfather was probably senile. His grandfather's only son - Henry 2d's father, Edsel - was dead, and one by one, Ford's most competent executives had been dismissed. Eventually, Mr. Ford's grandmother, Clara, put pressure on her husband, and Mr. Ford's mother threatened to sell her stock in Ford, which was then family owned, unless her son was given control. In September 1945, the 82-year-old Mr. Ford resigned, and his namesake took over. After Mr. Ford's palace coup brought control of the company, it took 10 years of hard work to rebuild Ford Motor into an industrial power throughout the world. In 1956, the family company sold stock to the public. Mr. Ford oversaw the creation of the modern Ford Foundation, dedicated to curing social ills and transforming society, and served as its chairman from 1950 to 1956. At first he stood up for the foundation's liberal efforts, but he lost control of the board and finally, in 1977, quit in disgust, complaining that it had an anticapitalist bias. Mr. Ford's social life became newsworthy as his marriage to Anne McDonnell, the mother of his children, faded in the late 1950's, particularly after he met Cristina Austin, the divorced wife of a British naval officer. In 1963 Mr. and Mrs. Ford separated and in 1964 they divorced; a large settlement was believed to be involved. In 1965 he married Mrs. Austin. After a decade with his second wife, Mr. Ford moved out of their lakefront mansion. He grew a beard and drank heavily, and his behavior became widely known when he was arrested and charged with drunken driving in California while with a Detroit friend, Kathleen DuRoss, whom he married in October 1980 after a second divorce. Mr. Ford's desire to keep his power brought him into conflict with his aides - a situation not unlike that in his grandfather's day. Henry Ford 2d was born Sept. 4, 1917, to Edsel and Eleanor Ford. He was the eldest of four children; there were two brothers, William Clay and the late Benson Ford, and a sister, Josephine. Mr. Ford is survived by his third wife, Kathleen; his son, Edsel 2d, and two daughters, Charlotte and Anne; six grandchildren, his brother William and his sister Josephine. He attended the Hotchkiss School in Lakeville, Conn., and Yale University, but did not graduate from college.