EXPLORER'S five-speed automatic transmission is standard with the V8 engine. A "smart" electronics approach with adaptive pressure control technology helps keep transmission shifts consistent over time, even as the transmission wears. The Control Trac 4WD system has been refined to make it more "transparent" to the driver, while improving its abilities in limited traction situations. The system has its own electronic controller, with enough computing power to allow Explorer's engineers to fine-tune the system to a wide variety of demands. For example, sensors measure and compare front and rear drive shaft speeds, as well as throttle position. This allows the system to incorporate the driver's intent into the mathematical formula that determines how much torque to send to each axle. These measurements are taken 50 times per second, for an almost seamless adjustment of the clutch that controls the transfer case output in the 4x4 system's "automatic" setting. If the rear wheels lose traction, the optimal amount of torque for the situation is transferred to the front. The system does not have to wait to sense slip before it takes action. For example, if the Explorer is sitting at rest in a four-wheel-drive setting and the driver presses the accelerator, the controller sends torque to both the front and back wheels within milli-seconds and then samples the results. This heads off wheel spin in low-traction situations. The Control Trac system includes a push-button switch - versus the former rotary knob - on the instrument panel that allows selection of 4x4 Auto, 4x4 High or 4x4 Low modes. In automatic mode, the drivetrain normally delivers all engine torque to the rear wheels. It uses an electronically controlled electro-magnetic clutch to redirect up to 100 per cent of engine torque to the front wheels when it detects rear-wheel slip or heavy throttle application. In 4x4 High the system effectively locks the front and rear driveshafts together to provide optimal traction of four wheels. In 4x4 Low the system locks the front and rear driveshafts together but adds a 2.48:1 gear reduction for extra pulling power. Built into the Control Trac system is a smart control, which can adjust for such variables as differences in tyre pressure. By continually tailoring torque transfer before any slip is detected, the system actually helps prevent wheels losing traction in the first place. The Control Trac transfer case housing is made of magnesium for reduced weight. Engineers also developed a new, lightweight magnesium transfer case that joins directly to the transmission. In the past, a 12.5cm aluminium adapter was used to attach the heavy transfer case, which invited unwanted vibration.