Auto Locking Hub operation

[RangerReviver1990]

So, I was thinking about this when i was removing at my shift motor from my transfer case. I’ve been told that the mechanisms to activate the hubs are all springs and stuff. But like, how would the hubs know when to activate? I don’t see any wires or anything. Do they activate when the front axle actually gets power to it from the transfer case and they spring into place?

 

[Josh B]

You can see it engage by turning the front drive shaft by hand. I first did this by accident, I somehow turned the front axle and saw the front drive springing (pardon the pun) into action. (it doesn't actually "spring") It simply moves into place as it begins to turn

 

[RonD]

+1 ^^^

Manual or auto hubs have a sliding gear that meshes with hub splines and axle splines, when this gear is moved out, hub and axle are not connected, disengaged, 2WD
When the gear slides in, hub and axle are connected, engaged, 4WD

Auto Hubs, 1997 and earlier, are torque activated
When the wheel/tire is powering the hub(2WD) then the gear slides out
When the axle powers the hub(4WD) the gear slides in

With manual you turn the handle to slide the gear in(lock) and out(unlock)

1998-2000 Pulse Vacuum Hub(PVH) used engine vacuum to pull the gear in for 4WD and a spring pushed it back out when there was no vacuum present
Maintaining a good vacuum seal inside a hub for many years, or even a few years, lol, proved to be unreliable