I had a problem with intermittent 4X4 operation, finally quitting altogether. If I switched vacuum lines @ the axle motor it would engage, but no 4X4 light. I have a '97 4.6 w/ auto and mechanical floor shift. I couldn't find any wiring diagrams, thought it was the GEM due to other problems, and finally took it in to be fixed at a reputable shop by "My Ford guy, he's good", according to the shop manager. Long story short, $425 later it is fixed. Turns out it was a bad switch on the drivers side at the front of the transfer case. This is the easiest thing to diagnose, and a 2 minute swap. Also apparently the last thing they checked, after 4 hours labour. So if your 4X4 isn't working, you get engagement of front driveshaft when put in 4X4, no front axle engagement, and switching vacuum lines works, and no 4X4 light is on.....save yourself some dough and buy a switch and see if it works, you might be ahead of the game. Oh, and maybe send me some of that saved dough!!!

Dan, who never has trusted shops, though I'm sure some are good