Planetary gearbox with three gear sets and drive couplings

The family of transmissions comprises a plurality of elements that can be used in drive trains to provide at least eight forward speeds and one reverse gear. The transmission family members include three planetary gear sets, which have seven torque-transmitting mechanisms and two fixed connecting elements. The powertrain includes an engine which can be selectively connected to at least one of planetary gear sets, and an output member which is continuously connected with another of the planetary gear. The seven torque-transmitting mechanisms provide connections between various gear members, the drive shaft and the transmission housing and ready to be operated in combinations of four to establish at least eight forward gears and at least one reverse speed.