US Patent 7163484 Eight-speed transmissions with four planetary gear sets

Eight-speed transmissions are provided that include four planetary gear sets having seven torque-transmitting mechanisms and various fixed interconnections to provide eight forward speed ratios and at least one 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 seven torque-transmitting mechanisms are operated in combinations of two. Reduced component speeds and improved ratios are achieved.