Ford breaks new ground with 10-speed automatic

BY Jim Kerr. Mar 10 04:00 am

Six-speed automatic transmissions have become common in many vehicles, with Chrysler and Mercedes offering 8-speeds in many products, but if you had asked me if we needed a 10-speed transmission, I would have answered no, that it was overkill — until I tried out the world’s first volume-production 10-speed automatic in Ford’s 2017 F-150 pickup. So what can 10 speeds do that other transmissions with less gear ratios can’t?

I had previously driven manual 10- and 15-speed transmissions, but these were in large highway trucks. All those gears were needed to get heavy loads moving from a stop while keeping the engine r.p.m. in its peak torque band. A 10-speed automatic transmission offers the same advantages of keeping the engine in the optimum r.p.m. range, but the automatic part means the driver doesn’t have to work at it — the computer programming does it all for you.

Ford’s 10-speed automatic is all new and Ford designed. It has a 7.4:1 gear ratio spread with the top three gears being overdrive ratios. For those readers not familiar with transmission language, gear ratio spread is the difference in gear ratios between the lowest gear and the highest gear. A wider gear ratio spread will have a lower first gear ratio for more pulling power or faster acceleration from a stop combined with a higher top gear ratio for improved fuel economy. Ford’s 10-speed automatic provides both with all those gears in between for smooth shifts and optimum performance at any speed.

Some of the transmission features include four planetary gear sets — many automatic transmissions use three planetary gear sets — six clutch pack assemblies and one over-running clutch unit. In the days of four-speed automatics, over-running clutches were common. They hold a part when rotating in one direction while spinning freely when turned in the opposite direction. This allowed the transmission to shift very smoothly because all that was necessary during a shift was to apply one clutch pack. Then the over-running clutch unit would instantly start to spin freely. The Ford transmission still has one over-running clutch but today almost all transmissions use clutch-to-clutch shifting, which means one clutch is released at the same time another clutch is applied. If the timing of the release and apply are not precise, then the transmission will either slip or bind and either can cause transmission failure. The Ford-developed software that controls the shifting is superb, with gear shifts that are almost imperceptible during acceleration and instant downshifts to lower gears when power is needed. The transmission computer monitors vehicle speed, accelerator pedal movement rate and position along with other inputs to determine what gear to select and can downshift from tenth gear directly down to third gear if necessary. I demanded full power acceleration and had it downshift from tenth to fourth gear several times and each time it was smooth and seamless.

The computer program also enables the driver to manually select gears and hold a specific gear, or with the transmission shifter in Drive position, the driver can select a lower gear with the button on the shift lever and this blocks out the higher gears until you wish to upshift again. This is a great feature for towing, which many F-150 owners do.

Other features of the new 10-speed automatic are an integrated electric fluid pump to keep transmission clutches engaged when the engine is stopped in the start/stop mode of operation, no cast iron parts to reduce transmission weight and the increased use of aluminum and powdered metal parts. The torque converter, which connects the transmission to the engine is also new, using an integrated lock up assembly that creates a direct drive from the engine to the transmission through the rear of the converter assembly instead of the front, which has been commonly used. This feature, along with careful design has created a transmission that is only about 25 millimetres longer than the previous 6-speed automatic transmission.

To accompany the mechanical and electronic designs, Ford has also created a new ultra-low viscosity transmission fluid to reduce internal drag which helps improve fuel economy. This 10-speed automatic transmission is paired exclusively with Ford’s3.5 litre EcoBoost V-6 engine in the 2017 F-150 and sets a new trend for the future.

james.kerr@sasktel.net