my buddies 90 four wheel drive quit working it will go into gear in the case but it no longer has four wheel drive any common problems with these trucks im not very up to date on much thast not first gen so any ideas will help thanks

 

Well uhhh.
Hubs locked?
Driveline in?
there could be a ton of things up..

 

id say make sure both hubs are locked

 

ADD? Getting vacuum to the servo so the sleeve on the front differential engages?

 

my 91 did the samw thing the easy fix is to install locking hubs then u can run a longer bolt into the detent hole on the bottom of the add shifter and the bolt will hold it in the lock or 4x4 position the use the locking hubs to engage or disengage the front axle