AWTF-80 SC

Gearset layout

A conventional 5-pinion planetary gearset and a compound Ravigneaux gearset is combined in a Lepelletier planetary gearset,^[1] to reduce both the size and weight. This means the Aisin AW TF-8# SC series is actually lighter than its five-speed predecessors.

Like all transmissions realized with Lepelletier planetary gearset, the AWTF-80 SC also dispenses with the use of the direct gear ratio, making it one of the very few automatic transmission concepts without such a ratio. It has a torque converter lock-up for all 6 forward gears, which can be fully disengage when stationary, largely closing the fuel efficiency gap between vehicles with automatic and manual transmissions.^{[citation needed]}

Gearbox control

To reduce external wiring as well as to provide a constant environment for the transmission control module (TCM), it is located inside the transmission housing. Gear shifting is managed by a computer program that oversees a clutch-to-clutch actuation that allows one clutch engage the instant the clutch from the previous gear disengages. When idling and with the foot brake depressed neutral gear is selected automatically. This helps to reduce internal temperatures and improve the fuel economy.

Improved fuel economy

The main objective in replacing the predecessor model was to improve vehicle fuel economy with extra speeds and a wider gear span to allow the engine speed level to be lowered (downspeeding), which is a decisive factor in improving energy efficiency and thus reducing fuel consumption. In addition, the lower engine speed level improves the noise-vibration-harshness comfort and the exterior noise is reduced. It has a torque converter lock-up for all 6 forward gears, which can be fully disengage when stationary, largely closing the fuel efficiency gap between vehicles with automatic and manual transmissions.

Reduced manufacturing complexity

In order to avoid a further increase in manufacturing complexity while expanding the number of gear ratios, ZF switched from the conventional design method—in which the planetary gearset concept was limited to a purely serial or in-line power flow—to a more modern design method that utilizes a planetary gearset concept with combined parallel and serial power flow. This was only possible thanks to computer-aided design and has resulted in a globally patented gearset concept. The AWTF-80 is based on the 6HP from ZF, which was the first transmission designed according to this new paradigm. After gaining additional gear ratios only with additional components, this time the number of components has to decrease while the number of ratios still increase. The resulting progress is reflected in a much better ratio of the number of gears to the number of components used compared to existing layouts.

Quality

The ratios of the 6 gears are evenly distributed in all versions. Exceptions are the large step from 1st to 2nd gear and the almost geometric steps from 3rd to 4th to 5th gear. They cannot be eliminated without affecting all other gears. As the large step is shifted due to the large span to a lower speed range than with conventional gearboxes, it is less significant. As the gear steps are smaller overall due to the additional gear(s), the geometric gear steps are still smaller than the corresponding gear steps of conventional gearboxes. Overall, therefore, the weaknesses are not overly significant. As the selected gearset concept saves up to 2 components compared to 5-speed transmissions, the advantages clearly outweigh the disadvantages.

The layout brings the ability to shift in a non-sequential manner – going from gear 6 to gear 2 in extreme situations simply by changing one shift element (actuating clutch E and releasing brake A).