A radially stacked planetary gear assembly provides improved lubrication fluid flow to the planet gear bearings of an outer planetary gear set which is especially important when the housing or outer planetary gear carrier is stationary. The assembly includes radially aligned or stacked inner and outer planetary gear sets each having a sun gear, a ring gear and a carrier having planet gears in constant mesh with the sun and ring gears wherein the ring gear of the inner gear set is also the sun gear of the outer gear set and the outer carrier is the assembly housing. The sun gear is disposed on a transmission shaft having lubrication passages which aligns with pluralities of radial openings in a hub housing. A circular plate or guide adjacent one side of the housing includes channels which align with the openings and functions as a lubrication director, channeling lubrication from the transmission shaft and the pluralities of radial openings in the housing hub to the outer bearings, shafts and planet gears.

A method of controlling an automatic transmission is provided. The automatic transmission includes a piston having first and second surfaces opposite from each other, friction plates, engaging and disengaging hydraulic pressure chambers for supplying and discharging hydraulic pressure and directing the piston to push the friction plates to be engaged and disengaged, a hydraulic pressure control valve for supplying and discharging hydraulic pressure to and from the chambers, first and second oil paths communicating the valve with the chambers, and a pressure reducing valve disposed in the second oil path and for preventing hydraulic pressure of the disengaging hydraulic pressure chamber from exceeding a given set pressure. The second surface has a larger area for receiving hydraulic pressure than an area of the first surface for receiving hydraulic pressure. The method includes changing the given set pressure according to information regarding a state of the automatic transmission.

A method for operating a vehicle drivetrain (1) includes decoupling, in the presence of a demand for realizing a sailing operating state of the vehicle drivetrain (1) during which a drive machine (2) is active and the power flow between the drive machine (2) and a drive output (3) is disconnected in a gearbox (4), the active drive machine (2) from the drive output (3) by opening of one of a plurality of shift elements (A to F) that is held in a closed operating state in order to realize the operating state present before the demand for decoupling of the active drive machine (2). The method also includes then actuating the plurality of shift elements (A to F) in a manner dependent on the present operating state profile of the vehicle drivetrain (1) and with the active drive machine (2) decoupled from the drive output (3).

A method for operating a vehicle drivetrain (1) having a drive machine (2), an output (3) and a gearbox (4) with the gearbox (4) arranged in power flow between the drive machine (2) and the output (3) includes opening, in the presence of a demand for activation of a sailing operating function of the vehicle drivetrain (1) and a simultaneously activated engine start-stop function, a positively engaging shift element (F) while the drive machine (2) is left both decoupled from the output (3) and shut down.

A method for operating a vehicle drivetrain (1) includes proceeding, in the presence of the demand for activation of the engine start-stop function of the vehicle drivetrain (1) and a simultaneously shut-down drive machine (2), from an operating state of the vehicle drivetrain (1) during which a sailing operating function of the vehicle drivetrain (1) is active, during which the drive machine (2) is decoupled from the drive output (3), during which the positively engaging shift element (F) is open and during which a rotational speed (n_ab) of the drive output (3) is higher than a defined rotational speed at which a rotational speed difference between shift element halves of the positively engaging shift element (F) lies within a rotational speed range within which the positively engaging shift element (F) is transferrable into the closed operating state, and actuating the positively engaging shift element (F) in a closing direction no later than when the defined rotational speed is reached.

A transmission (G) includes an input shaft (GW1), an output shaft (GW2), an electric machine (EM), a plurality of planetary gear sets (P1-P3; 2P1-2P5), and gear-implementing shift elements (S1-S6; 2S1-2S5). Via engagement of a first of the gear-implementing shift elements (S1, 2S1), which is a force-locking shift element having a variable torque transmission capacity, the input shaft (GW1) and an element (E1, 22E1) of one of the planetary gear sets (P3; 2P4) can be brought into a fixed rotational speed relationship with respect to each other. Another element (E2, 22E2a, 22E2b) of one of the planetary gear sets (P1, 2P3, 2P5) is permanently connected to a rotor (R) of the electric machine (EM). By engaging an auxiliary shift element (ZS, 2ZSa, 2ZSb), which is a form-locking shift element, the rotor (R) and the input shaft (GW1) can be brought into a fixed rotational speed relationship with respect to each other.

A family of transmission gearing arrangements provides between eight and ten forward speed ratios and a reverse speed ratio. Three planetary gear sets are located on the input axis and a fourth planetary gear set is located on an offset axis. Axis transfer gears convey power between the input axis and the offset axis. One axis transfer gear is supported by a front support while another is supported by a center support. The center support also supports a clutch module and supplies pressurized fluid to engage the clutches in the clutch module.

A three mode continuously variable transmission (CVT) for a motor vehicle includes an optional speed change device connected to a pulley and a belt assembly or other continuously variable unit. The pulley and belt assembly is also connected to a planetary gear set arrangement. The planetary gear set arrangement generally includes two planetary gear sets, two brakes and two clutches. The planetary gear set arrangement is connected to a final drive unit. Engagement of the clutches and brakes provides three modes of operation to the CVT.

A transmission (G) is provided having four planetary gear sets (P1, P2, P3, P4), several shafts (W1-W8) and a first, second, third, fourth and fifth shift element (B1, B2, K1, K2, K3), the selective meshing of which brings about different transmission ratio relationships between a transmission input shaft (GW1) and a transmission output shaft (GW2). The transmission (G) includes a sixth shift element (K4), through which the fifth shaft (W5) is connectable to the sun gear (So-P4) of the fourth planetary gear set (P4).

Provided is an automatic transmission including: an input section to which power generated by a drive source is input; an output section configured to output a drive force; and a gear shifting mechanism configured to change a gear ratio. The power is input to the input section without intervention of a hydraulic power transmission device. The gear shifting mechanism includes a predetermined frictional engagement element for achieving a starting gear ratio of a vehicle. The frictional engagement element includes: a plurality of friction plates arranged with clearances therebetween; a piston movable between a releasing position where the friction plates are brought into a released state, and an engaging position where the friction plates are brought into an engaged state by pressing the friction plates; and an urging mechanism configured to urge the piston so that the piston abuts against the friction plates and the clearances are reduced.