ok so my 4wd does not work and from testing everything else is good and i know its something wrong in the front diff i think it is the switch fork in the front axle/front diff connection area but i was curious if anyone has taken apart the front axle before. if u have could u give me specific details on how to take it apart? pics would be really good too if u have them.

 

I've got the How To saved for the rear diff, dunno about the front one though...I would assume its somewhat more challenging with all the steering/stabilization parts up there..anyone have pics?

 

ya the front and rear diff r very differnt as to how they hook up since u have more goin on up in the front

 

What all have you tested? Does the vacuum actuator under the battery get vacuum and does it pull the cable?
Have you read this thread?
https://blazerforum.com/m_52228/tm.htm