It's actually a pair of solenoids mounted on the firewall just inboard of the windshield wiper motor. I did a manually actuated valve conversion to fix the same problem I was having and it works perfectly. I'm still working on a writeup that I'm hoping to have done fairly soon here. I've been real busy lately and went home on leave last week so I haven't had the opportunity to get the last few pics I need for it.
I think they are under the fuse panel, or at least in that general area. The ones with a silver looking top, I am going from memmory. I think they have a little hole in the top to reset them. In the beginning I thought it was my relay that was causing the cruiser not to shift out of 4 wheel drive. But like everybody else it was the soleniod on the firewall. Good luck.