Ford: ford f-150 overdrive switch, ford f 150, fuse panel

Question
I have a 2002 f-150 w/ 4.6L V-8.  When I hit the switch on the end of the shifter to turn the overdrive off, it blows the fuse in the fuse panel underneath steering column.  Any idea about what might cause this sort of thing to happen.  It only blows the fuse when the truck is in a forward gear.  

Answer
I think id have to say that there are shorted wires in either the steering column or going to the transmission. the column ones are easy to see by removing the upper and lower shroud of the steering column inspect the small black wire coming from the shifter have seen them wires like to break on the top of the column. There also could be underneath wiring issues that as well take a peek under your truck if you do not see anything with the column. Hope this is any assistance.

Jim