4WD is really a 2WD, and a 2WD is really a 1WD. With an open diff, or even a LSD, when one wheel has all the traction, and the other one doesnt, the wheel in the air will spin, and the one touching the terrain will sit there. With LSD, depending on how tight it is, it might still transfer enough power to the wheel with traction that it can still pull you out of certain situations.
Only way to make a 2WD into a true 2WD, and a 4WD into a true 4WD, is to use either Detroit Lockers, or On Demand lockers like an Eaton E-Locker or an ARB Air Locker. This locks the diff carrier solid, so it's like having a solid axle. This is the only way to truly make both wheels on an axle recieve full power from the ring gear.
And just as a note, I have a Detroit Locker on my 96 Ram, and it's 2WD, with 31" A/T tires, and sand pwns it. Truck layed on the frame in some sand the minute it touched some. Took a 1 ton dually about an hour of trying to get me pulled out it was sunk so bad. My exhaust tips were even underground. I also tried taking it through some minor mud and hills, and still a no-go, buried that effer to the frame again. Had to bum a ride back to our shop where I worked, and got my coworker's toyota Tacoma 4WD. He put it in 4 Lo and popped that truck out like it was nothing.
Shit, I even got my truck stuck in my own back yard. Detroit locker, A/T's, and it was stuck and the tires were only in an inch or two of mud, and it just sat there, couldnt go backward or forward, rocking didnt help, it was held solid. I ended up getting my other truck, and two 25,000 lb ratchet straps that made it up to the concrete parking lot so my other Ram could get some bite, and had to pull it out of my back yard. Pretty sad really.
So yeah, 2WD is NOT for offroading. You might get away with some pseudo-off roading with your 2WD, as long as you have some good off-road tires, and are not in any mud or unlevel ground, that's about as far as a 2WD goes. Otherwise, get a 4WD.
My 2WD 4Runner will stay firmly planted to the pavement, it's not meant for off road, was not designed for it. It's really a stripped down un-capable off road vehicle, that's now just a good lookin mommy wagon for the wife and kids. That's what a 2WD is really meant to be.
