ZF Squeezes 3% More Efficiency from 8-Speed Gearbox

ZF Friedrichshafen AG says its second-generation 8-speed automatic transmission is 3% more fuel efficient than the original gearbox.

The new 8HP unit benefits from lower drag torque, thanks to a revised multidisk shift system. A new gearset reduces the rotational speed across all gears by an average 50 rpm, resulting in 1% gain in fuel efficiency.

Internal oil-pump pressure had been lowered from 5 bar to 3.5 bar, thus trimming the system's energy requirement. The transmission's coasting function has now been expanded to work at speeds as high as 99 mph. And an improved stop-start system works faster to shut off the engine .

ZF's modular 8HP gearbox can be configured to handle torque ranges of 300-1,000 newton-meters (221-738 lb-ft) and fit the powertrains of everything from plug-in hybrids to four-wheel-drive vehicles.