Sometimes when you need a Terminator, a crazy puppet backpack will do. Sometimes, you've just gotta go a little further. And when it came to Terminator 3, the effects team took the second option and basically built actually Terminators. Almost.
In this behind the scenes video from the always-enlightening Stan Winston School, some of the minds behind the machines in Terminator 3 explain their process, and the takeaway is that there is/was at least one, fully-drivable T-1. All that's missing is the bullets. And the orders to kill.
And hey, if you are going to leave two things out, those are probably good ones to pick.