Not a Jeep guy but I do have a question

[JMach1]

Merry XMas. I dont have a Jeep, I am a Toyota guy, but I do wheel with a bunch of friends that have CJ's and wranglers.
My In laws have a 1999 Jeep Grand Cherokee, V6, 4X4 and a automatic with auto locking hubs. On XMas eve they got the Jeep stuck in our drive way, I walked out and told my father in law to just put it in 4 wheel drive and back out. He informed me that his Jeep has to be moving forward to put it in 4 wheel drive. We argued about it while I shoveled the rear tire out and got him un stuck. My wife drives a front wheel drive Hyundai that made it up our drive way after our blizzard. So really he was not stuck in a drift, he was just stuck on a icy spot with his rear wheels.
My question is, do you really have to be moving forward to engage 4 wheel drive
on his Grand Cherokee?
Because if you drive in 2 wd on the dry streets and then turn onto one of our streets that has not been plowed and get stuck, what the heck do you do?
I think that you can put it in 4x4 while stopped but that is why I am asking you guys.
Thanks
JMach1

[83yoda]

yeah you can ingage it my buddy has a 98 grand cherokee limited and with there 4wd all your doing is engaging the transfer case so you dont have to be moving.

[95toyota]

This is true you dont have to be moving to put it in 4wd however you do have to be moving for the auto locking hubs to lock into place.. so your both right..

[copycat]

Just to add to the confusion, do the Jeep hubs require backing up to unlock like my dad's Blazer does?

We have often wondered if they can unlock while backing up in 4x4 or if they only disengage when there isn't any torque applied.

My guess is that if you were to put the Jeep in 4x4 and then try to go forward or backward the hubs would "mesh" and lock as the front axles would rotate. It certainly wouldn't hurt anything to try.

[95toyota]

Well if there anything like toyota Auto locking hubs, when your in 4wd and back up, they unlock, roll back a few feet then lock back in.. but that few feet of 2wd in the rocks doesnt help..