fixed front wheel u joint now 4x4 wont work
 

i swapped out a new ujoint in the front right wheel. Now I cant shift to 4x4 on the fly (have to come to almost a complete stop) and 4x4 doesnt seem to want to engage,

I suppose i'll have to strip it down to the axle again and when I do what should I look for? I am a novice and any help would be greatly appreciated.

2006 f350 fx4 diesel 2 door.

p.s. manually locking hubs