F150 Not shifting correctly?

[Splitshot]

I have a 2006 F150 with 255 hours on it that is not shifting properly/at all. It seems to be stuck in forward gear right now. The throttle moves freely and so does the drive linkage. The linkage in the motor housing also appears to be moving into the proper locations for Forward - Neutral - Reverse too, but nothing happens. It's stuck in forward.
What's more strange is that the motor starts and stops with the turn of the key - perfectly, but it is in forward gear, so a start puts you into motion right away. Usually, the electronic safety will not let you start in gear, but this does.
The motor will go WOT in forward and reduce down to a fine idle too - like normal, but it won't shift out of forward. All other motor functions also work just fine and I have no warning lights or buzzers going off at all. Anyone have any ideas on where to start with this?
Thanks.
Splitshot

[Sequoiha]

Ill bet the cable is broken inside the housing, disconnect the shift cable at the engine and pull on it, bet it comes out in your hand,,

[Splitshot]

Cables are all attached. The linkage inside the motor for both the throttle and for shifting move when the lever is moved forward and reversed.

Since writing the original post though, I did some more digging and found a shift linkage arm near the front lower part of the motor that had come off the swing pin (missing cotter-pin to secure in place). This arm connects to the shifting link that goes to the gear housing inside the motor. Once I reconnected that and installed a new cotter-pin, I was able to shift again. However, upon starting the engine and shifting into gear(s), I heard the uglyest gear-grinding sound ever. It was somewhat difficult to shift into gear too, so I'm not sure if this had something to do with it all or not. Nevertheless, I shut it all down and scheduled some time with my technician. I don't want to make a bad situation worse at this point. ....Time for the experts to take a look.
Thanks.

[Sequoiha]

good that you found it, when you shifted it into gear, did you slow shift it or quickly put it in gear, if it was slow we call this granny shifting, these lower units are not syncronized and you cannot shift slow. you will get grinding noise.