In Baja, the Mexicans put rocks in the back of their pickups (if they are otherwise empty) to improve traction... VW beetles (the air cooled ones) were fantastic off road becaue the engine was in back, over the drive wheels! The Baja Bug and VW powered dune buggies were a direct result!
The last race I went to was in laguna salada. There was a somewhat steep decline we came down and would eventually have to go back up. Later, We saw a group of jeeps and 1 ford ranger go up the incline. A couple of the jeeps made it up in what seemed 2wd, a few stopped midway and must have engaged 4wd, and poor old Ford Ranger has his rear tires spinning like crazy, so engaged 4x4. This made me nervous as we were by ourselves with no locker or 4wd. All I have to say is that I crawled up the incline without the slightest feel of wheel spin... Mechanical LSD and weight in the back of a TOYOTA FTMFW!