Ravigneaux planetary gearset

The gearset provides four forward gear ratios and reverse by braking or restraining various elements of the mechanism.

By choosing a set of components for held, input, and output, the planetary gear will increase or decrease speed and change direction.

As originally invented, the Ravigneaux puts two planetary gear trains on a single planet carrier.

The original patent application proposed that electromagnetic clutches be used in the transmission.

The year of the patent was 1949, a time when pressure operated hydraulic technology was less well developed.

Several years later, when the Ravigneaux went into production at Ford Motor Company, hydraulically operated band brakes and clutches were used.

The photos on the right show the planet carrier from a Ford FMX automatic transmission.

Not shown are the two sun gears, called primary and secondary, that rotate within the carrier.

Also not shown is a ring gear, also called an annulus, having internal teeth fitting around the carrier.

Multiple planets, turning in the opposite direction and meshing with different sun gears, gives the Ravigneaux the ability to provide multiple speeds and reverse, with just one set of planetary gears.