Multiple speed automatic transmission for automotive vehicles

摘要

An automatic transmission for an automotive vehicle includes first and second simple planetary gear units (44,54), certain of whose elements are continually interconnected and certain others are releasably connected through operation of friction elements and one-way couplings. The input shaft (26) of the transmission is adapted to drive elements of the planetary gear units (44,54) through an underdrive gearset (30) and an overdrive gearset (36). The various speed ratios result by either underdriving or overdriving an element of the planetary gear unit (44,54) or both underdriving one element and overdriving another element. Several parallel torque delivery paths include a series arrangement of the overrunning coupling in parallel with a friction element. This arrangement permits engine braking during coast conditions when the coupling overruns. The overdrive gearset (36) is available to produce a speed ratio without involving the planetary gear units (44,54).