Jack Nicklaus's changes in 1980 were nowhere near the same as Woods changes with Haney or Foley. Jack put out a very good book detailing the changes in the early 1980's. His problem in the late 1970's involved swinging too steeply with the arms and club, and failing to release the clubhead as he had done at his best. (his words) He tended to block the ball. His book and articles in golf digest in 1980 detailed the changes. He set his head at address more in the middle of his stance, not off the right leg. He stood taller to the ball, not as bent over from the hips. He tried to take his hands back to the inside more, with a deeper backswing in his terms. He certainly was nowhere near as flat as Woods has become in the backswing. On the downswing, he let his left knee straighten thru impact more to allow him to sling the club. In all, his swing did not change as significantly as Woods, his teacher Jack Grout had told him he was losing his timing due to his not pivoting fully. Nicklaus was not a practicer, from September to January, he did not pick up a club typically. Grout introduced the swing changes in January, he won the US Open in June, with the PGA to follow that year. In 1986, he wrote of changing again, swinging more upright, reaching for the sky on the backswing and follow through. From 1970-1986, there is little real change to his swing. Prior to 1970 it looked different because he weighed forty pounds more. I think Woods changes thru the years have been more significant than any player in history that was not hit by a bus.