Also on the jeep.com site you will find other information like 4X4 Basics under "For Owners".2H to 4H or 4H to 2H
Shifting between 2H and 4H can be made with the vehicle stopped or in motion. If the vehicle is in motion, shifts can be made up to 55 mph (88 km/h). With the vehicle in motion, the transfer case will engage/disengage faster if you momentarily release the accelerator pedal after completing the shift. Apply a constant force when shifting the transfer case lever.
I admit I don't normally reverse, but reversing when shifting back into 2wd helps to take the tension of all the components and make sure everything unlocks properly. Otherwise when you drop it back into 2wd and you keep going forward, sometimes it takes things a bit before they loosen up enough to release (if the components are under high tension, they can't release properly). This can result in stuff breaking if you take a tight turn before everything has released and something binds up.To my understanding you can shift into 4 hi at any legal speed I believe is what I read. 4 lo I always am stopped or at a creep. I never have had to reverse or any nonsense like that in my jeep. That's why jeep tj 4wd is the best I've ever seen. Simple to use and it shifts very easily. The np 231 t-case is awesome IMO.