HELPING HAND: Dual clutch unit bolts on the front and engages dual input shafts.
HELPING HAND: Dual clutch unit bolts on the front and engages dual input shafts. David Meredith

Dual clutch technology gain

I'VE seen some pretty good drivers in my time, especially those who run daily regional freight in hilly country with an 18-speed Eaton Roadranger manual transmission.

Keeping momentum on hills is the holy grail of fuel-efficient driving and on-time deliveries.

So missing a gear or taking time to get the revs right just costs money as the speed drops several km/h while you mess about with the gear lever.

The current crop of AMT transmissions helps with that process, but I know of many drivers who can still almost match it with an AMT.

The latest Scania and Volvo boxes are very hard to beat, particularly when the electronics are used to squirt some engine brake into the process to bring the revs down faster.

But short of the full torque-converter automatics such as Allison's TC10 and ZF's equivalent, which are both full automatics configured for linehaul, there's been little prospect of keeping full torque at the drive wheels as the gears change. Until now - in Europe at least.

Volvo now builds a dual clutch version of its superb I-Shift transmission for use with its 13-litre engines.

I drove the new box pulling 60-tonnes of 6x4 rigid and dog on Volvo's test track in Gothenburg recently and couldn't help a smile as I imagined churning up the M1 from Sydney to Newcastle waving at the Cummins, CAT and DD15 powered Roadranger dudes that I'd be passing up the hills.

I-Shift is a conventional constant mesh 12-speed unit that's turned into latest technology through electronic modules, add-ons and control units. But the dual clutch version adds a double input shaft.

Currently it's only available with the 13-litre engine.

There appears to be a torque limit on this first version, however we can anticipate the dual clutch system will be available with the 16-litre engine at sometime in the future.

My rig started at a normal throttle setting, and the changes occurred about the same rate as the standard I-Shift transmission.

But when I pushed through the indent into kick-down mode, the transmission displayed another character entirely.

I stopped on a 12% grade, engaged hill-hold, and then flattened the throttle.

The gearbox went through the first six ratios with no apparent loss in torque.

There was the usual short AMT delay when the gearbox shifted from the bottom box into the top range (from sixth to seventh), but from then on it was fast shifting all over again.

The double clutch assembly is attached to the front of the standard I-Shift gearbox.

In simple terms, the alternate clutch engages the next gear in advance and drive switches immediately to that shaft where the gear-set is already meshed.

At normal throttle settings, a new countershaft brake and software speeds up the shifting process to reduce torque interruption.

Ultimately this is one automated manual gearbox that can threaten the dominance of Allison's automatic for specific truck applications.

It could even mean a 13-litre engine will do a similar job to a 16-litre unit, or at least much closer to it.

The Australian release has not yet been determined.

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