Toyota Repair: transfer case, southern california desert, vacuum hoses

Question
i have a 1990 4runner 4x4 and the transfer case goes in 4hi and 4lo fine, the front drive shaft spins when its engaged but the front tires dont pull, im thinkin its a vacuum line or something. do you have any idea what would make the front hubs not lock?

Answer
Yes, I'm very familiar with this problem since I used to own a 1990 4-Runner a few years back. The problem in most cases is that one of the vacuum hoses has come off at the actuator on the front differential, remove the front rock shield for inspection, if the hoses are still connected it's a good possibility that the metal pipes going into the actuator are clogged with rust, you may be able to clean the pipes out with some stiff flexible wire or you can do what I did and remove the actuator and clean the lines and then applying vacuum with a pump to the lines to verify operation, the vacuum chamber actually moves a shift sleeve to engage and lock the front differential, the switch that indicates when it's in 4x4 is attached to the differential and if the 4x4 indicator light on the dash doesn't turn on it's not in 4x4. I was unfortunate enough to have 4x4 not engage in a remote area(southern california desert) got stuck in deep sand before realizing that 4x4 did not happen, sleeping in the front seat of the 4-Runner is not so bad, no food but the cooler full of beer helped?