1993 Chevy S-10 4WD does not work

Manual Transfer case or electronic?

With the transfer case in 4wd can you turn the front drive shaft?
If you can still turn the front drive shaft with it in 4 wheel the transfer case has a problem.
If the shaft won't turn in 4 wheel but the front axle isn't locked then you have a problem in the front axle interlock. Check the vacuum switch on the transfer case.
You should have vacuum on one line, Vent on another line (Teed in with the transfer case vent) and the last line goes to the axle interlock actuator. The vacuum line starts at a connection at the rear of the engine under the distributor. Then down to the switch. The interlock should pull in when vacuum is applied to it. If the actuator isn't moving you have a vacuum problem.

Sounds like the encoder motor has a problem. It is possible to check it if you have the book. The test is a lot to type out.

Yes the manual box from a 83 up S series will bolt in. They used the same trans and parts. The only real difference is the actuator method.