Help on switching transfer case fluids!!

[KivaKid]

I have a 1980 Cherokee with the NP208 part time transfer case and 258 4.2L I6. I believe the PO has 10W-30 in the NP208, as recommended for the early '80s. I searched and found a post that said New Process changed to ATF later on, and even suggested that the original ones that used 10W-30 could change over. Is this true? And also, what EXACT ATF should I use? Dextron I, II, III?? I know our F*rd vans at work have been sensitive to getting the wrong fluid, just a difference of I to II, etc.. It's cold in the morning here in CO, so I thought it might loosen up shifting a bit when cold, and it needs to be changed anyway. Any special process to make sure to get all the oil out, or a little mix won't hurt? :confused:

[Bob Barry]

The later cases take Dexron II/III, so you can pump your case full of that. I don't imagine a little mix would hurt anything; just cause a slight change in viscosity.