4x4 not engaging in my 96 150 with auto lock hubs...?

Shift indicator comes on. Transfer case engages. Drive shaft is turning. When shifted into hi or low 4, front axle can still be turned manually.

Problem seems to be in front differential? Does the 96 operate on a similar system to the 97 and up that I read about on the other thread? I'm not to familiar with it, since I haven't owned the truck very long, but it seems different from what some were describing for the 97.

Any and all help would be much appreciated!

 

Help?