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. The
Lexus IS F and
LS 460 (with sport package) use Sport Direct Shift (SPDS) which allows for faster shift times. The torque converter can lockup from 2nd to 8th gears.
Reduced manufacturing complexity In order to avoid a further increase in manufacturing complexity while expanding the number of gear ratios,
Aisin 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. 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. Smaller parts and a hydraulic circuit with fewer components allow the transmission to maintain the same size as the previous LS 430's 6-speed transmission. The aluminum
die-cast case is 10% lighter, yet 30% more rigid, even with two additional gears and a 22% greater torque capacity. The new transmission weighs or 10% more than the previous unit. With new micro-laser technology gear tooth production tolerances have been reduced by 50%. Aluminum has also replaced steel on gear tooth surfaces. Shift times are as low as 0.35 seconds or 41% faster than the previous LS 430's unit.
Two reverse gears The gearset concept offers two reverse gears. Due to the increasing electronic control of automatic transmissions and engines, a fast reverse gear (i.e. designed to reduce wheel spin) is no longer necessary for problem-free starting in icy conditions (winter mode). It is therefore unlikely that car manufacturers will make use of this special option of a dedicated winter mode with an additional reverse gear R2. For this reason, the representation of R2 in the tables is shaded gray throughout. In some data sheets, the gear ratio of R2 is given, presumably a careless error. The direction is reversed in gearset 3, the outer one of the Ravigneaux gearset. In the fast reverse gear R2, this part of the Ravigneaux gearset is directly connected to the input (turbine) side. To reduce the shaft speed for an appropriate reverse gear R1, the input (turbine) is put through gearset 1 first. This reduction corresponds to the ratio of the 3rd gear. Therefore, the gear step between the two reverse gears reflects the ratio of the 3rd gear.
Quality All 8-speed automatic transmissions from Aisin and Toyota for passenger cars are based on the same layout in both engines orientations. For transverse installation, the layout of the longitudinal installation was merely mirrored. Gearset 1 is not an ordinary one, but a
reversed one. It consists of 2 pinions that mesh with each other. One of these pinions meshes with the sun gear, the other with the ring gear. As a results, the gearset generates different ratios and the sun gear rotates in the same direction as the ring gear when the planetary gear carrier is stationary. This made it possible to manage 8 speeds with 3 gearsets. As a result, the transmission is more compact than 8-speed transmissions from competitors. This means that an 8-speed automatic transmission was also possible for transverse engines. == UA 80E/F failures and problems ==