I have a 1997 F-150 4x4 with a manual shift. The Gear shifter is stuck in 4th gear. This happened one time and it popped out after a little jiggling...but this time it is stuck good. It was acting normally up till this happened. Could it be a bent or worn fork? Is there any way to "unstick it" without dropping the transmission out completely? Any tricks or suggestions?

More info....Acted normally up till this happened...no warning. It went into gear just fine. It is in gear as it will move forward if I give it enough gas and ease out the clutch. It is in 2wd right now.