98 4Runner clunking noise

1998 Toyota 4 Runner SR5 Auto, 4WD, 131,000 miles. Has been maintained per manufacturers schedule. Only problem thus far has been the replacement of the oil sensor sending unit (vehicle was leaking oil). No "4 wheeling". Only normail driving. Has been driven primarily in the city.

My problem: When I am turning LEFT at slow speeds (as at an intersection), I hear a loud clunking sound coming from under the car. I can feel it. It sounds like someone is under the vehicle with a hammer. It does not occur when I turn right, only left. At normal low and high speeds straight ahead, there is no problem. Vehicle runs good otherwise. Sometimes the clunking is very loud and sometimes not so loud. Thanks for any help. PS I made a "small donation".