4 wheel drive high wont engage

I have a 94 s10 blazer and the 4 wheel drive high will not engage but the 4 wheel low will. When the 4 wheel low does engage it feels like it works then it slips or something. Does anyone have an idea what is going on is the transfer case goin bad or what?

please do a search on this forum for 4x4. There has been numerous threads about this topic. But what I would definately check first would be vacum. But please search the forum I am sure you will find more information as to what to check.

use the search feature.