Transfer Case
WARNING: This page is about a different car, the 1988 Jeep Wrangler, 1988 Jeep Wagoneer, 1988 Jeep Grand Wagoneer, 1988 Jeep Comanche, and 1988 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
Check transfer case fluid every 12,000 miles and replace fluid every 30,000 miles.