I am going through the same thing,,,,,,,was out roughing it and it went haywire, if i find anything before anyone else i will post it, have done continuity test on dash switch, next is limiter switch on side of t-case selector motr...
'99 ranger 4x4, 3.0, 31.50x15's 2 inch lift stock suspension automaic all electric shift vacumn hubs
Ok, here is what I found with mine, hope it helps others, that shift is built like the old generators on the old cars, when the comentator gets packed with brush dust, it does not like to work so good.
I took my motor apart ( there are instructions on how to do this in the tech library), I used a single sided razor blade to scrape all the brush dust out of the slits in the brass commentator and then use fine emery cloth to polish it back up (just like we done on the old car generators) and then used electronics grade compressed are to blow all the dust out.
trans-case works great now.