German transmission-maker ZF has revealed more details on its all-new eight-speed dual-clutch auto gearbox developed with Porsche, for rear- and all-wheel-drive applications starting with the new Panamera.
The DCT, dubbed a "modular hybrid transmission kit", offers quicker shifts than its predecessor, the potential for greater economy, and future-proofs its applications by better-incorporating electrification.
Thanks to a new gearset design, it was possible to integrate a 100kW hybrid module without increasing the length of the transmission. The peak torque ceiling is a massive 1000Nm.
There's also the potential for an integrated all-wheel distribution option, driving the front axle using a hang-on clutch.
Power loss is said to be reduced by up to 28 per cent thanks to a higher gear spread, an additional ratio (giving it two overdrive gears), a demand-driven lubrication system and a new electronic transmission control unit mounted externally.
The new transmission is available for front-longitudinal configuration in four different variants (standard, all-wheel drive, hybrid, all-wheel hybrid) in three torque classes, to a maximum of 1000Nm.
A traditional bugbear of some DCTs has been their torque ceilings.
The torque class is defined by the configuration variety of the dual-clutch modules, with the basic transmission and gearset always remaining the same. This is also true for the transmission hydraulics, shift system, parking lock and control unit, including software.
To make the transmission as compact as possible, a new gearset concept with two countershafts and one summation shaft was constructed. The fixed gears, which are all located on the transmission input shafts, can be used several times, resulting in less wheel levels, making the basic transmission significantly shorter in length.
"This was the only way to maintain the required length of the hybrid module and integrate it into the limited installation space," ZF said.
This gearset architecture offers another advantage. Based on the modular concept, it is not only suitable for front-longitudinal applications but will also be able to cater for other driveline configurations.
ZF has also customised a hybrid module for the optional variant, including a torsional damper, a separating clutch with actuators as well as the electric motor. It can be integrated directly into the clutch bell housing.
This does not alter the dimensions of the overall transmission but has considerable impact on its properties. With 100kW peak output, 55kW continuous power and 400Nm torque, a vehicle can accelerate up to 140km/h on pure electric power alone. With this technology, all other hybrid functions are also possible – from recuperation to boost mode.
With the all-wheel drive variant of the 8DT, an integrated all-wheel distributor transmission transfers torque to the front axle gear as needed. The hang-on, all-wheel clutch is designed as a wet multidisk clutch.
This new transmission is manufactured at ZF’s Brandenburg, Germany plant and volume production of vehicles featuring the 8DT began with the Porsche Panamera