This may seem like a silly question, but did you take all of the weight off of the front end or jack it up? You can then experience any loose movement, especially vertical movement with the kingpins. Leave the tire on the car and try rocking the wheels back and forth, grasping the tire with both hands - 12 o'clock/6 o'clock position, then 9/3 position. Also move the steering wheel to where you hear the clunk. This may show wear in the steering box, idler arm, tie rods or kingpins - there's not much else left. One last thing, make sure the stabilizer bar ends are not broken or loose where they mount to the frame.
--
Cam a.k.a. CVOLVO.COM