front diff lock cable works, yet front dif doesnt lock in. '89 S10 blazer two door 4.3

 

It sounds like the cable is not actually pulling the actuator in the front axle into place. I'm not sure but I think on that model there are only 3 bolts (or 5) that hold the cover in place on the right side of the front diff. You can take the bolts out and pull on the outer cable to check if it's attatched to the actuator.
Can you hear the actuator "click" when the cable is pulled by the vacuum diaphram under the battery?

 

well, i ended up replacing the cable because it was rusted and stuck. yet when i went to engage the front axle manually, all i heard was a slight clunking noise. is that a splined collar that locks the axle? is there anyway i can get rid of the foolish set up. its not a daily driver, though i do drive it to the trails. the whole thing really seems pointles.

 

That slight clunking noise is probably the actuator working. To check the actual repair, you can jack up all 4 wheels to test for 4 wheel drive or just do a short accelleration in 4 wheel drive on a soft surface of grass or gravel, and check the tire marks.

I believe Hanr3 has a post with pictures for installing a direct cable to the actuator to engage the front diff.
Check some of the posts referring to diffs or trannys over the last couple of days. If you find it, great, if not I'm sure you could just ask him, or I could search for it.