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

 

Will the hubs lock manually?
Don't know how you are determining the shift on the fly is not working.
How did you know before the work was done?