Will not stay in 4WD or 2WD

Hi All, new here.

Just got a 93 S-10 Bazer Tahoe for free. only issue were the exhaust from Cat back needed replacing (done with a flowmaster to boot). next is the thing keeps flipping from 4wd to 2wd, any suggestions on the fix for this?
Oh it is the electric switch not the shifter. saw an excellent how 2 here on hoses and actuator (will check next weekend)
But can there be a diferent issue?

Teck

IS IT A S-10 BLAZER OR BIG BLAZER OR S-10 OR A TAHOE?

What transfer case tag on back will id it.
And what does the shift buttons say on them?

It's probably an S-10 Blazer with Tahoe package = fully loaded.

That's what I got most of the parts for my Bravada from in the junkyard...

It is the 93 S-10 Blazer tahoe Package

switch says 4wd and 2wd i believe?

We need the transfer case type.
Look on back of it and post the id no off of tag on back.
Is it just a 2 button shift button deal?
How many shift buttons and what do they all say?

Willl have to grab that later