I'm having the EXACT same symptoms that Skymac is describing, on the same truck (98 Blazer). I'm fairly convinced that the TCCM is the issue because I can here a click coming from it, and there is no movement, sound, or any signs of life past it along the line. This afternoon I completly removed the TCCM and I'm hoping to find somewhere to test it. Anywhere (other than dealers with inconvient hours) that might be able to tell me something? AutoZone, Advance, Napa. . .any ideas?
Looking around on the net it seems that a lot of these trucks with electronic 4WD have issues. GM never did a recall on this did they?