Used Rockwell T136, 2.5 Ton Military Transfer Case Air Shift Unit. These are the newer versions and do not have the sprag bearings that are prone to failure. These are very robust and basically an oversized NP205.
1:1 High Range
2:1 Low Range
High/Low operated with cable or lever
2WD/4WD operated via air actuator or can be permanently locked in 4WD (Fails to 2WD)