(FORTUNE Magazine) – The mother of all executive transitions is underway at Citigroup, and for Sanford I. Weill--who by his own choice left the CEO's job on Oct. 1 while staying on as chairman--this change in his life was initially a powerful shock. He'd been going "180 miles a hour," he reminded FORTUNE as 2003 drew to a close, and suddenly he was down around "zero." His days yawned: "I'd have this meeting at nine in the morning and be doing a phone call with someone at 12," he says, "and at 9:15 I'd be asking myself, 'What do I do until noon?' " He gestured at his spacious, picture-packed quarters on the third floor of Citi's Manhattan headquarters. "There are only so many times I can pace around this office."

Since the first frustrating weeks of the changeover, Weill says, he has found ways to fill his time "much, much better." In particular, he has expanded his work on some of his outside interests, including Weill Medical College, Carnegie Hall, and the National Academy Foundation, which fosters career-education programs for teenagers. Weill also has a new outside preoccupation: a big 154-foot motor yacht that has a crew of nine and was built especially for him.

But you don't do yachts at the office, of course, and even now it can't be said that Weill has jammed his calendar. The problem of downtime is compounded because the new CEO, Charles "Chuck" Prince, 54, and certain other executive buddies of Weill's took the transition step of moving their offices to the second floor. That leaves Weill deprived of an easy opportunity to do what he really likes, which is walk around and schmooze. Couldn't he walk downstairs and schmooze? He could, he says, but he's been trying to give Prince and Citi's president and chief operating officer, Robert Willumstad, a chance to have him out of their hair. In fact, he has not gone to any of Citi's weekly management meetings (which Prince runs), and amazingly, he stayed clear of this fall's budget process.

Weill's official time with Prince and Willumstad is a once-a-week breakfast, at which they mainly talk big-picture stuff ("I've gone from micro-micro to macro-macro," Weill says wryly), or he raises questions about the daily, weekly, and monthly figures he sees. Unsurprisingly, big outliers in the figures put him on the phone between meetings. "I'm still a very big shareholder," he says.

For his part, Prince sympathizes with Weill's withdrawal pains. After all, says Prince, we have here both a type A personality and a founder of the business. But Prince says Weill is being scrupulous about letting the new team run things and clarifying how much weight his own opinions should be given. "He's adopted a certain phraseology," says Prince. "He'll say 'Now, I might think x, but of course it's up to you two to decide.' "

Tough as it all has been, Weill says he has absolutely no doubt that he did the right thing in giving up the CEO's job. With only minor breaks, he'd been running businesses for decades and thinking about the job 24/7. He's particularly glad now not to be burdened with the quarterly pressure to show earnings gains. "I honestly think," says Weill, "that I was ready to pack it in."

Of course, there are some stray details arising out of Wall Street's legal problems that Weill, as chairman, still needs to think about. Weill once vowed that until Citi's legal hassles were completely settled, he'd go on what he has called the "Eliot Spitzer diet"--no martinis, bread, or desserts. Today, with many but not all of the problems resolved, Weill has modified the diet (and has a few more pounds to prove it). Says he: "I'm still not eating bread or desserts." --Carol J. Loomis