Technical director Sam Michael has revealed that the decision to create the smallest gearbox the team has ever used has been key to the radical rear end on the FW33 unveiled to the public in Valencia.

The car, which will be fully launched in its 2011 livery later this month, features an aggressive design on the rear compared to rival machines in an effort to help airflow to the rear wing.

Michael revealed that work had been going on on the design of the rear of the car for nearly twelve months to finalise how the car would appear, with a pull-rod suspension set-up also in place.

"Like most other teams, the target is to have as much clear flow to the rear wing assembly as possible," he said. "It is clear that we have lifted the top wishbone and track rod, and opted for a Z-bone layout, which was commonly used in the early 1990s. Using a pull-rod was an easy decision for our particular design, as it means there's less blockage to the rear.

"This is the smallest and lowest gearbox we have ever made, with the most extreme driveshaft design. We made all these major decisions in March 2010 and have subsequently worked hard to ensure reliability through plenty of mileage on the dyno."

Another key part of the design is the new adjustable rear wing, with Michael revealing that Williams has managed to get its system working 'within milliseconds' of the driver pressing the button on his steering wheel.

"With a hydraulic system, we're down to a few milliseconds to activate," he said. "When the driver comes off the button or applies the brakes it returns to the high downforce position. While testing the system in the simulator, we asked the driver to hold the button down and allow the system to automatically bring it back when applying the brakes, but there were certain situations where you want the driver to bring it back before he touches the brakes."