One problem related to axle shaft has been reported for the 1999 Toyota 4Runner. The most recently reported issues are listed below.
This is the 4th time in 4 years that my 4runner has had a left rear axle seal problem. The vehicle only has 69,000 miles on it, so this problem arises about every 11- 15k miles. Each time the seals and breaks have to be changed. The axle shaft was replaced last time, but I am still having the same problem. There are tons of people with this very expensive recurring problem and its ridiculous that Toyota knows about it but don't do anything.