1999 Chevy Astro clunk noise

Could be a worn, or loose suspension component. If you raise each front wheel with weight supported under the lower control arm, you may be able to feel looseness when the wheel is grasped and rocked at 12 and 6, and also 9 and 3(clock position). I would suspect a ball joint or control arm bushing, but you may find wheel bearings, or loose steering components as well.