Ravigneaux Planetary Gearset - Ford FMX Ravigneaux Example

Ford FMX Ravigneaux Example

The opening for the sun gears is resting on a table. A dinner fork is shown for scale. An internal-tooth ring gear (not shown) meshes with three of the planet gears. The ring gear turns the drive shaft.

The photos on the right show the planet carrier from a Ford FMX automatic transmission. The planet carrier is the central part of a planetary gear set. 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. Input power is applied to one or both sun gears, and output power is taken from the ring gear, which turns the drive shaft.

The FMX transmission is controlled through two clutches and two bands, called the forward and rear clutches, and the forward and rear bands, respectively. The clutches and bands are operated by hydraulic pressure. In this case, forward means closest to the engine. When applied, a clutch connects a rotational component to the engine, causing the component to turn, and a band holds the component, preventing it from turning. The forward clutch controls power to the primary sun gear. The rear clutch controls power to the secondary sun gear. Confusingly, the band that holds the rear clutch is called the front band. The rear band holds the planet carrier.