[bigblockv6]

Fulltime 4wd first came out in 1973 as in the Jeep Quadratrac and the fulltime Np203 used by GM and Dodge. Older trucks with out locking hubs were still part time systems. I don't think you realize the whole idea of a 4wd system preceded the idea of locking hubs. During WWII all the Jeeps running around had no hubs but were a part time system and it wasn't t until the mid 40's that Arthur Warn came out with a hub system that allowed the front end components not to spin will in 2wd mode, yet that was a crude system because it required swapping the front outer drive flanges with ones that weren't splined that way the front axles shaft would not spin and neither would the ring & pinion and driveshaft. By the 50's Warn finally invented the first locking and unlocking selectable hub. Ironically today many 4wd's offer on demand part time systems for shift on the fly 4wd so the use of selectable hubs has diminished, the disadvantage of that is all the front end components are turning along with the front driveshaft, some have an axle disconnect system that disconnects one side and that just turns the spider gear eliminating the extra drag.