ZF says the new ‘8HP’ transmission has been optimised for the requirements of modern engine technology with a focus on downsizing and downspeeding, as many engines are now turbocharged, feature fewer cylinders and produce their maximum torque at a very early stage.
The company claims a number of developments have helped improve the transmission’s efficiency by up to three per cent.
ZF says the gearsets have been optimised and now have a higher spread (from 7.0 to 7.8), which it claims reduces speed by 50 revolutions per minute and fuel consumption by one per cent.
Internal losses have also been reduced by the introduction of new multi-disc separation strategies, with additional springs integrated into the multi-disc packages to ensure the friction shift elements are almost fully opened and cause less drag.
The transmission’s oil pump now operates with a reduced pressure, down from 5 to 3.5 bar, requiring less energy overall.
A new innovation of the 8HP is the clutch is now fully opened during deceleration and when the vehicle is stationary, which ZF says means it is now no longer necessary to “‘brake’ against the drive”.
The transmission’s ‘coasting’ function – the uncoupling of the gearbox and simultaneous stopping of the engine – now operates at speeds up to 160km/h. ZF has also further optimised the stop/start function, with the engine now stopping immediately as the vehicle stops, rather than waiting 1.5 seconds as in the original eight-speed.
New advanced torsional vibration dampers claim to eliminate the vibrations that occur on the engine side, isolating them from the driveline and the body.
The second-gen ZF 8HP entered volume production in July, debuting in the BMW 520d as the 8HP50 version that is designed for torque outputs up to 500Nm. An 8HP75 version will join ZF’s portfolio in the future for torque outputs up to 750Nm. ZF says the transmission will eventually be rolled out in more than 1000 different automotive applications.