Abstract: A planetary transmission mechanism comprising two simple planetary gear sets driven by the engine of a vehicle through an input clutch or torque converter and having five friction engaging devices and two one-way engaging devices to establish four forward driving ratios and reverse through the transmission. A center output gear is mounted between the input clutch or torque converter and the planetary gear sets. The friction engaging devices comprising clutches associated with the planetary gear sets are mounted immediately adjacent the gear input elements which they connect. A pair of one-way devices are provided for various of the ratios which have a common outer race member.