Geek Speak

When it comes to gears, how many is too many?

Motor (Australia) - - CONTENTS - By JAMES WHITBOURN

We spill the beans on Lexus’s 10-speed ’box

THE WORLD’S car mak­ers are of­ten sheep-like in their adop­tion of ve­hic­u­lar fash­ions. How­ever, they – and trans­mis­sion man­u­fac­tur­ers – cer­tainly aren’t aligned on the best way to trans­mit power.

With the tra­di­tional man­ual on the wane, the jerky robo­tised man­ual, po­ten­tially un­re­li­able dual-clutch auto, bor­ing CVT and even the hum­ble torque con­verter auto have all been of­fered as the trans­mis­sions of the fu­ture.

And it’s the lat­ter that Lexus is set to adopt for its forth­com­ing LC 500, which is due next year. The grand tour­ing coupe, which is based on the LF-LC con­cept car shown at Detroit in 2012, will fea­ture a 10-speed auto.

It joins the likes of the 2017 Ford F150 Rap­tor and 2016 Chevro­let Ca­maro ZL1 in hav­ing 10 ra­tios.

The un­der­ly­ing aim of the new gear­box is fuel econ­omy, though the mar­ket­ing ben­e­fits of a 10-speed can’t be over­looked.

But will it bring a per­for­mance ben­e­fit and, if so, how? Well, if you can keep an en­gine in the meat of its torque band, you’ll max­imise the car’s ac­cel­er­a­tion. It’s this sim­ple prin­ci­ple that spawned the closer­a­tio rac­ing gear­box back when 'boxes only had four or so slots.

Closely stacked cogs stop the revs from drop­ping off, which is par­tic­u­larly help­ful for highly strung en­gines that make their power high in the rev range. On the other hand, there’s the time lost do­ing all those gear changes – the Lexus would do sev­eral in the sprint from 0-100km/h.

More im­por­tantly, in terms of driver ap­peal, will the boxset of 10 go down as a mo­tor­ing ‘best-of’ or pale along­side the clas­sic open­gated man­ual?

Well, the ex­pe­ri­ence of rid­ing a big whack of torque, us­ing just one of two ra­tios, is one of the most de­li­cious el­e­ments of pi­lot­ing a bi­gengined, tall-geared car on a tight and twisty road. Think Com­modore SS on a favoured slice of moun­tain tar­mac, blast­ing from cor­ner exit to en­try in sec­ond and third…

The 10-speed ex­pe­ri­ence could be a mega-miser, its progress punc­tu­ated by a road-train-like con­stant swap­ping of cogs – or, the changes will be so smooth it’ll just feel like a CVT (with­out the wideopen-throt­tle drone).

If the man­ual is dead and mul­ti­ra­tio 'boxes waste time shift­ing gears, surely the CVT is set to rise? In the­ory, it could, how­ever the

"Lexus's LC 500 joins the F150 Rap­tor and Ca­maro ZL1 in hav­ing 10 ra­tios"

CVT is not nat­u­rally a high-torque de­vice, and any­one who has driven one knows why even the big­gest CVT pro­po­nents are now giv­ing their gear­boxes ar­ti­fi­cial ra­tio steps to mimic a con­ven­tional auto.

While hav­ing a con­tin­u­ously vari­able gear ra­tio beats, well, pick any num­ber be­tween seven and 10 ra­tios (in the spec-sheet con­test, at least) an elas­tic throt­tle and dron­ing power de­liv­ery has no home in the hi-po car.

Time will tell whether the 10-speed slusher does.

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