Volvo 960 sedan, 1997

This 960 is pushing 150K miles, is in good shape, and well maintained. I have replaced the swaybar links, and entire muffler system.
Still, I hear clunking under car as I drive over rough road. My mechanic says there is nothing loose underneath. It’s a sweet car and much fun to drive. With rear wheel drive it turns on a dime. How can I solve the annoying clunking noise?
Thanks for your help JRP

Sway bar links are not the only part of the suspension that clunk. Worn struts and strut top plates can also cluck, worn out spring isolators can cause a clunk (rubber plates on top and under the spring on the strut), as well as lower control arm bushings, ball joints, and tie rod ends. Besides suspension, motor and transmission mounts are suspect, as well as core support and sub-frame bushings. The car is 15 years old with 150,000 miles on it. All bets are off.