This is a post I did some time ago on diagnosing transfer case shift problems. Because my truck is a 2004 and yours is a 2000, the fuse #'s won't apply, and when I talk about a 4WD control module, you will have a GEM module instead. However the rest should apply.

https://www.ford-trucks.com/forums/1...l#post10605244

Shift motors do go out. More often the problem is one of the relays though. Try the diagnostics in that post and see what you come up with.