Here you can see a close-up of a T-Lock locking differential and a Traxxas shock. The differential is "open" by design, but can be locked remotely, via the controller. When "lock" is selected, a servo pushes a steel rod that is connected to the arm you see at the bottom of the diff. This action locks the gears in the differential to split the torque evenly to both axles. The 87mm, hard-anodized, Teflon-coated shock is easily adjustable.