The clanking is probably a worn out universal joint on the driveshaft, or a worn out rear axle gears. All very common on these. I used to have a 95' Suburban SLT.

Try this Chevrolet/GMC truck forum for more help. This is the link to the 88-99 truck forum. Many other forums there covering ALL of the Chevrolet cars and trucks.

http://www.chevytalk.org/threads/postlist.php?Cat=0&Board=UBB70

Good luck!