got into the truck this morning at 5am. Deep snow all around. 4WD is a must, me thinks.
WRONG!!, could not engage 4WD as either the transfer box or the vac system was frozen solid

The light just kept flashing and the 4H / 4L shift wouldnt budge. Had to swtruggle in 2WD for nearly 20 miles until it warmed up then it all worked perfectly.
Anyone heard of this happening before?