US Patent 7226381 Nine-speed transmissions with four planetary gear sets

Nine-speed transmissions are provided that include four planetary gear sets having six torque-transmitting mechanisms and various fixed interconnections to provide nine forward speed ratios and a reverse speed ratio. The powertrain includes an engine and torque converter that is continuously connected to at least one of the planetary gear members and an output member that is continuously connected with another of the planetary gear members. The six torque-transmitting mechanisms are operated in combinations of two. Reduced component speeds and improved ratios are achieved.