Tuesday 5 March 2013

Daimler readies nine-speed gearbox

JaguarLandRover (JLR) will not be the only European passenger car maker to offer a nine-speed automatic transmission. Daimler in Germany is working on one too that will appear first in its AMG offering and other large cars.

Daimler’s Mercedes transmission plant at Stuttgart Untertuekheim is currently the scene of much activity as some of the latest machine tools are being put in place ready for the start of production.

All the machines delivered to the plant have passed pre-acceptance trials in vendors’ plants. The implication is that they have achieved both quality and cycle time criteria for one of the Europe’s most demanding customers.

Meanwhile, production begins this year of ZF’s nine-speed transmission, the 9HP, at the company’s Greenville, South Carolina plant in the US where planned capacity is of the order of 400,000 units a year.

Launched in 2009 at the IAA in Germany, the 9HP is designed for transverse front-engined vehicles and thus is suitable for both front-wheel drive and 4x4 vehicles – hence Land Rover’s interest. As such, ZF claims the 9HP can be used in three-quarters of cars produced world-wide.

The 9HP uses four individual gear sets. ZF claims the 9HP also uses for the first time dog clutches for power shifting. The overall ratio spread is 9.8 to 1 and this, it is claimed can enable 0-60 mile/h times to be cut by 2s. Fuel consumption can be improved by 10 to 16 per cent. At a cruising speed of around 75 mile/h engine revs are cut by some 700 rev/min leading to lower cabin noise for occupants.

The 9HP will be available in two model ranges covering a toque range of 150lbft (203Nm) to 355lbft (481Nm)

The qualities achieved by the 9HP will, no doubt be mirrored by Daimler’s nine-speed ‘box when it appears.