transmisson? 2004 f150 fx4
 

i have a 2004 f150 fx4 5.4l 3v triton with about 57k on it. my problem is when im going and say i had to slow down for a stop light and i got down to about 15-25 and i went to gas it again it will sometimes feel like its in "neutral" and it just revs until about 3k then clunks now ive only clunked it one time. i changed fluid and filter no sign of any metal on the magnet in the pan. anyones help would be appreciated.

also only seems to do it with overdrive on