Automatic for the people: The story behind ZF’s eight-speed gearbox

"I don’t change manually, I have to admit!"

Didier Manning is one of ZF’s chief engineers as well as its key liaison with BMW, a major user of the German company’s transmissions.

He drives an X5 daily yet despite its eight smartly stacked ratios – and shifting speeds similar to those of the ZF 8HP’s dual-clutch rivals – he feels little need to get too involved himself.

We’ll be the first to point out that ‘8HP’ is a very underwhelming name for a gearbox that’s been adopted with such breadth; you’ll find versions of ZF’s blockbuster hit in a relatively cheap BMW 1 Series, a silky smooth Rolls-Royce Phantom and a number of Dodge’s unhinged Hellcats, plus all manner of cars that squeeze into the ginormous gaps between that trio.

It's now into its fourth generation, with numerous evolutions during its 15-year life helping ease it into a new era of electrification. ZF’s now ubiquitous eight-speed automatic launched in 2008 via its debut in a new generation of 7 Series, but its development process started several years earlier, amid an automotive landscape that was quite different.

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ZF 8-speed

Back then: Across ZF’s home market, manuals still dominated and the only excitement around auto shifters concerned the recent dawn of dual-clutch units – DSG having just launched to great acclaim in the VW Golf R32 and Audi TT 3.2.

I ask Manning if his employer had forecast an upward curve in the demand for autos on the horizon. "I wouldn’t say it was accidental but obviously, we are happy the tendency went in that direction," he says. "But one mustn’t forget we still do manual gearboxes. The BMW M2 and M3 have a stick shift for the purist at heart.

"We’ve had a strong heritage with BMW from the 1960s onwards as our systems integration partner. This enabled us to have a robust architecture that we could use in a lot of different applications and this is definitely something that helped us achieve success with the 8HP.

"The gearbox can go from 200 to 1000Nm without any visible difference from the outside. With our fourth generation, we’ve bridged e-mobility from within the gearbox."

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ZF has certainly never rested on its laurels, constantly adapting the 8HP to market demands – current and future.

It’s worked especially hard to integrate the extra components of hybridisation within its transmission so that the overall unit takes up no more space than before.

This is welcome news to any car-makers that are hastily adding batteries and motors to their internal combustion cars, as it allows them to retain the core chassis architecture to help fast-track products to launch.

"It is a hell of a challenge when it comes to vibration profiles and the integration process," Manning confirms. "To make it work we’ve had to minimise the size of the oil pan and so the whole oil feed process has changed to cope. That was one of the big challenges during the development phase that we’ve thankfully mastered.

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"It went into production last year for mild hybrids and has won awards as the most efficient generator you can have in a 48V MHEV system. Now we’re going into production with a plug-in model."

The company is also ensuring it stays flexible as we muddled folk try to work out whether it’s an EV, hybrid or pure combustion engine that suits our needs in an increasingly complex market. ZF’s Saarbrücken plant (close to Germany’s western border) produces up to 10,000 transmissions a day and all iterations of the 8HP currently share the same line, at least until the trends of car buyers become more predictable.

But there were challenges to master even before the dawn of electrification; every gearbox that rolls down the line has a unique tune for the specific model it’ll eventually meet.

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"Take apart a fourth-generation 8HP and you’d find the sort of cogs normally found in a watch," Manning adds.

"To combine these processes with that kind of volume is something we’re extremely proud of. Production ramped up very quickly in the early days and we make gearboxes not just for Europe, but the rest of the world, where there aren’t the same discussions when it comes to electric vehicles.

"Still, we’re curious to see what’ll happen over the next couple of years. We still see a future beyond 2030 for internal combustion engines. Someone who does 50,000 miles a year is still more likely to use a highly efficient ICE or fuel cell car than an EV."

Naturally, ZF is open-minded when it comes to the automotive world’s next chapter and will remain agile so it can mirror what’s needed. "Our ambition is to have the same position in the e-axle world as in the gearbox world," says Manning. "With the 8HP we managed to develop a specification that covered a lot of requirements.

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"In the e-mobility world, the car-makers play a completely different role, no longer making their own engines by default and so deciding what to do themselves and where to buy in components. To have a product that is technically sound but also financially viable is not easy and a lot of people are fighting for this market. What we’re driving for is a modular kit to cover all the needs of our many customers."

While the 8HP made waves thanks to its extra two ratios over contemporary rivals at launch, the same simply won’t be true when it comes to ZF’s take on modular EV transmissions. "The maximum number of speeds we’re discussing is two or three," Manning says. "You don’t need more. Even then it’s only important in a Porsche that’ll do 300km/h.

"If you’re looking at mass production vehicles, there’s not yet an apparent need beyond one gear."

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Does that mean he thinks EVs with manual transmissions, a technology Toyota has given us a glimpse of, are something of a curious endeavour? "Yes, to be honest. There is no efficiency gain."

He's adamant that ZF got it bang on with the 8HP, though. So why the jump up from six gears, which was the industry standard for most gearboxes 15 years ago?

"We needed a cutting edge. A solution which was intelligent in its use of an ICE. We didn’t want a span that wasn’t useful, which is why we went to eight rather than nine or ten speeds. It’s pointless fitting more as you won’t use them all and you’re just carrying more weight around.

"The driveability was improved in such a way that you don’t need to change gears yourself, as it anticipates what you’d be doing in manual driving. So for either speed or comfort, the system integration allows you to determine which gear you want purely with your right foot, which you’ll master after driving your new car only once or twice."

"As soon as you’ve experienced that, you never go back to a manual."

Which probably explains why he never wants to shift himself.

🛞