4x4 help, transfer case works, hubs don't

[Dr.Destructo]

Hi;

As you can tell by my other posts, I am currently certifying a 1983 Chev Blazer 4x4 305ci

The 4x4 doesn't work. It has limited slip on front and rear.

The guy I bought the truck from (for $400) said that 4x4 worked, but when I jacked it up to investigate, I found that:

The transfer case engages no problem. However, the front wheels don't turn in 4x4.

I would imagine that this is a problem within the hubs.

Wondering if any of you can specifically mention which part may be broken that would stop the wheels from powering.

I have the service manual, but I want to research these problems before I start taking the hubs apart.

Thanks