Clunking sound from passenger front

My '98 Windstar (105K miles) just started to have this clunking sound 2 days ago.

I found out that the clunking sound is only happening during:
1. Big Right Turn
2. Above a certain speed ~20MPH so that the van is loaded on the driver side.

I tested this in a big empty parking lot, I circle my van CW around a light pole. If below a certain speed say like 10MPH, the van does not make any sounds. But once I make it a bit faster ~20MPH, the right front is making some clunking noise.

So what is it? I searched and found all sorts of answers. Due to the speed-related of my case, I do not think it's the CV joints. What else?

Thanks!

I would start by checking the front end compotents. Check the ball joints, tie rod ends and such. Normally a bad cv will click when making turns but would not hurt to check for torn cv boots.

One thing that can cause this is the busing working loose where the rod.....that has this bushing on it passes through the subframe.......
It is the part with the BIG nut on it......under the oil filter in this picture.
http://rides.webshots.com/photo/1324733856011220610fHHHrI

A popular way to repair it is by welding it.......
I had the job done for me....at the FORD dealership.
Here is a picture that was sent to me by a forum member who did the job himself.
http://rides.webshots.com/photo/2527378610011220610BgMIon

I paid $700 for 1 dealership to weld it.....they saw me coming.......and it lasted less than 1 year (about 6 months).
Then I paid another dealership to weld it again....... $150......and it has lasted over 10 years.

you could also look at your sway bar bushings. They typically last about 30,000 km for me and there certainly is a clunk when they're in need of replacement. Generally the passenger side goes bad first as that's the side with the most pot holes.