Planetary gear, animation: Function
WARNING: This page is about a different car, the 2005 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.
To obtain the different gear ratios, the component parts of the planetary gears, such as the sun wheel, planet wheel, ring wheel and planet carrier are locked or released respectively. The friction elements for this are all disc type except for brake B4 which is band type. As there are four different planetary gears, it is possible to obtain a wide range of different ratios.