One problem related to rear suspension springs has been reported for the 1999 Ford F-250. The most recently reported issues are listed below.
I recently was at a Ford dealer for a transmission related problem. While there I noticed that there was a leaf missing from my left rear leaf spring pack. When I mentioned it to the mechanic he said. Oh yah, we've had to replace a lot of springs, they just keep breaking. He said if I looked on them I would notice that they were made in mexico. He said Ford has been replacing a lot of springs.