One problem related to transfer case has been reported for the 1999 GMC Safari. The most recently reported issues are listed below.
During acceleration from a stop, when braking, and when going around a corner a very noticeable clunking noise was heard coming from the front end of the vehicle. Dealer had to contact detroit about the problem and found out that an improper fluid was placed in the awd transfer case at the factory and that the fliud should be flushed and replaced with the new fliud(part no. 12378508). The clunking had also caused the transfer case mounting bolts to become loose probably from the vibration. This service was performed at no cost and have not noticed any similar problems since. The vehicle now has approximately 5200 miles on it.