Clunking noise in 1999 Ford Ranger

I have a 1999 Ford Ranger, V-6, 2WD,70500 miles. It has a clunking noise that sounds like it is coming from the front or near the front of the truck. You can only hear the noise in hot weather, and after the truck is run for a few miles. The longer you drive, the louder it gets. I have replaced in the front suspension : upper and lower ball joints, upper and lower control arm bushings, Sway bar bushings and links, outer tie rod ends, shocks, and coils spring insulators.
I removed the driveshaft and cleaned and greased the splines, and replaced the back shocks.
I did some of this work myself, but had it to my Ford Truck dealer do most of the work, and had him check over what I did. I have had this noise for over a year, and no one can find the source, not even the Ford shop.
I have been over the entire truck several times and everything looks fine, and the Ford people agree.
As I stated this is only in hot weather. I live in Florida, so we have a lot of hot days. In the mornings if it is 60 degrees or less, I can drive for half an hour and not hear a bit of noise.
The noise sounds like when a stabizer bar is loose, or exauhst is clanging against the frame. But both of these items have been checked several times.
I'm sorry this post is so long, but I wanted to give as much detail as possile. Thanks, BillJ

What about brake calipers or brake shoes. I also look at frame mounts

check the pullys on your accessories ,water pump,alternator ...ect  possably might be something in the tranny. 
hell if worse comes to worse and you never find the problem . get a loud stereo and crank it loud !!!

Sway bar to frame bushings?  Seems to be a common problem on a bunch of other ford products.  Also explained a little with temp.  With cooler temp that bushing will clamp tighter to sway bar than when temp increases and swells rubber.

Hi, Sorry it took so long to get back to you, but I wanted to try a couple more ideas before I posted back. I replaced all the sway bar bushings and links with Ford OEM and then with Moog, but it did not help.  I'm sorry to say  I am about out of ideas. Nothing I have tried has helped. The only other idea I'm thinking is maybe in the rack and pinion steering  after the fliud gets hot. I have checked the rack for any inner tie rod play when the rack and pinion is cool, and found none. I have had a few other people contact me with this problem, but no one has a solution.