One problem related to brake disc rotor has been reported for the 1999 GMC Safari. The most recently reported issues are listed below.
Front rotors turned @ 16,000 miles due to shimmy. Pads were not replaced. No cost-covered under warranty. Vehicle now has 29,000 miles and shimmy returned. Dealer replaced pads/turned rotors and replaced shoes/turned drums at my expense. (not covered under warranty). I believe that this is excessive brake wear and the manufacturer claims that this is normal wear and not covered. Vehicle now has rotors that were turned twice. Guess who going to pay again (for new rotors) at next pad replacement.