Technicaly no.
They are automatic 4x4.
The truck will drive in 2wd only until rear wheel slippage is detected. Then power is automatically transferred to the front.
There is a mod in the sticky part of the modified 3rd gen forum. The Brown Wire Mod (BWM). Putting a switch in this wire will allow you to prevent activation of the front wheels and keep the truck in true 2wd.