One problem related to clunking noise has been reported for the 1999 Toyota Avalon. The most recently reported issues are listed below.
At 39,00 mi. My 1999 Toyota Avalon makes alot of noise under the vehicle, vibrates at any speed on less than smooth road, vibrates on freeway at 70 mph. Loud clunking noises. Car dealer replaced front struts and aligned front to no avail.