Well, I've done some more research and I think I've answered my own
question. Please let me know if any of this is in error:
Prior to 1967 Kaiser/Jeep made 2wd and 4wd Wagoneers. After 1967
only the 4wd was produced. These were all part-time 4wd that continually
turned the drive train and necessitated manually locking the hubs for
4wd. AMC introduced Quadra-trac in 1973, which allowed you to shift into
the drive train but you still had to manually lock the hubs into 4wd. These
were quieter and got better mpg. Selec-trac, introduced in 1983,
eliminated the locking hubs with a dashboard switch to engage 4wd.
I'm not particularly interested in the Command-trac, etc. of the later
years. Is this right?