The DynaMax AWD coupling is basically like some others in that an electric motor operates an oil pump to pressurize a housing with a multidisc clutch. The hydraulic pressure applies the clutch so required torque is transferred from the front-drive-based system to the rear differential—the greater the pressure, the more torque is shifted to the rear.
also explains the gradual disengagement of the AWD lock after 19mph.
If the pressure must be increased (for more torque transfer to the rear), the motor turns forward to operate the pump. If the front-end traction is good, the computer simply backs off the motor-pump assembly to reduce clutch-apply pressure. Then more torque (and if it's appropriate, all the torque) is delivered to the front wheels. There are no pump valves to open and close.
The computer algorithm for the clutch looks for consistently good front-end traction and when possible will maintain 100% to the front wheels for fuel economy. The algorithm, however, is adaptive; in "sporty driving" it will apportion torque as needed between front and rear, Sackl said, and it will transfer 100% to the rear if appropriate.
The Sportage has a tow capacity of 2000 lb (907 kg); Kia's testing showed that even with maximum loads, including hill climbing, the coupling's internal temperature never reached a thermal shutoff level. A contributing factor is the cooling provided by the large oil capacity of the DynaMax housing, Sackl said.
The fluid fill, unlike competitive designs, is life of vehicle, he added.