Your landcruiser has 3 differentials. The button with the stick figured drive train and the X in the middle is the diff lock button for the center diff. That diff locks the front and rear driveshafts to spin at the same speed. If you lock the diff on dry pavement, your front and rear tires are spinning the same speed and you bind them and risk breaking something. The front and rear differential locks are a different story. The differential locks that your going to have to install in your diffs basically lock the right and left tires to spin at the same speed. This causes binding in one of your diffs and loss of control.
Main reason a locking diff was designed is so you can keep momentum while one tire is in the air and the other is on the ground.
And in my case, a locking diff helps me do some tight donuts
Then again, this is why Toyota and other car manufactures introduced advanced traction control systems. So the owners with little to no experiecne wont have to push the wrong button and break a diff or lose control.
Traction control, especially Toyotas A-Trac works very very good. Soo good that I myself can't live without it. Both my 4Runner (although my 4Runner has the first generation Traction control) and my FJ do very well offroad. The FJ, LC, LX, GX, 4th gen 4Runners ATRAC works soo damn good, it reacts almost immediately and at the correct speeds.
I was playing with my FJ in some offcamber hills. If you apply light or medium throttle at around 2,000rpm, ATRAC kicks in very well, but when you floor it, ATRAC disables and you can spin them tires through the mud like its nobodies buisness.
Heres a demo of how well the ATRAC works. Watch the tire movement.
http://youtube.com/watch?v=ZknBx8T0KwI
