possible Transmission problem?
 

I have an 07 5.4 and just recently I started havin shuttering and alittle knock between OD and 3rd gear. it happens when OD is around 1100-1300rpm right before it downshifts to 3rd. past 1700 or so it runs like a champ, and its just b/t OD and 3rd... any answers out there??