HELP!! 4X4 Problems 2001 Explorer Sport 4.0 V6

I'm in need of some assistance with this one. While engaged in 4X4 High ( No problem in low) Going down the road or stopped in park, the vehicle will click in and out of 4 wheel. I say this because you can hear a click coming from behind the dash on the passengers side, The dash light will go out and you can feel it. I have chased down vaccum lines with no luck in finding any leaks. I have been dealing with this problem for about 3 years now and i would like to resolve this. Where do i start? Where is the 4X4 Module located?

It looks like the Electronic Shift Control Module will be left of the center of the instrument cluster, kind of above the accelerator pedal. It gets inputs from the GEM module.

Quite a few others on this forum have experienced issues with the shift motor, have you searched the forum to see if others have isolated symptoms like yours to the transfer case shift motor?

-Rod