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Dual Clutch Deletes Delays

Updated: Jan 16, 2020

Late in 2017 Volvo introduced a dual clutch option for its renowned I-Shift transmission at the company’s proving ground in Gothenburg Sweden. The FH13 prime mover and trailer test included a hill start on about an eight per cent grade with 55-tonnes on board. The drag on the truck would have been enough to defeat the conventional I-Shift’s change speed, and I’d have been doomed to drive the entire hill in low gear.

However the dual clutch system allowed me to accelerate up the hill through the first six gears. From sixth to seventh the range change is ‘normal,’ then it’s back to some slick shifting. Apart from a much faster ascent, and fuel saving from lower rpm, the strain on the truck’s powertrain was vastly reduced.

Around the metropolitan and regional areas, particularly in traffic or hill climbs, this new box is likely to deliver substantial cost benefits, as well as a boost to driver satisfaction.

Since the Sweden drive, local Volvo engineers have been validating the option in unique Australian applications and conditions.

It’s now available on the Euro V 13-litre engine in either FM or FH configurations, with 500 or 540hp.

I drove it on the steep, several kilometre climb up Cunningham’s Gap in Queensland to the plateau of the Main Range. It was a perfect place to stretch the new transmission and assess its benefits over a conventional I-Shift.

Getting the B-double set through city traffic was itself a test of the new shifter, with tight corners and merges on to the freeways. I’d set the shift lever to auto so that I could see how the internal smarts handled rapid on/off throttle movements and undulating connecting roads.

The new box weighs an addiitional 101kgs. It’s added on the production line at Wacol, and has arrived becasue of strong interest from customers. The dealer network has also encouraged Volvo to get it to market here, as it’s the only dual clutch gearbox available for heavy vehicles. With approved oil (Volvo’s), the oil change interval is 450,000kms.

Volvo’s engineers have essentially split the conventional i-Shift box into two, with seperate input shafts running alongside each other. One handles the odd numbered gears and the other the evens. A dry clutch operates each shaft. The engine and gearbox management software pre-selects the next gear while the gear in use is delivering torque, spinning the cluster so it meshes and can instantly transfer the torque when a shift is made.

The result is an almost seamless torque flow through the two ranges of the 12 ratios.

If nothing else mattered, I’d calculate the around $10,000 extra cost would be recovered within a couple of years, depending on application. But in my view the driveability is worth it anyway.

The test truck was an almost brand new 540hp FH13, so things were a bit tight, but the driveline was still very smooth. On the flat and with sporadic traffic, I engaged adaptive cruise control and set the distance monitor to almost maximum distance.

As the roads led into merging traffic, the system engaged the exhaust and engine brake to maintain a safe distance. As things slowed down further, the transmission changed down to boost the engine braking effect. Significantly, even those changes were almost instant, maintaining a steady retardation rate for maximum safety.

Livestock operators in particular would be impressed with the smoothness, even if the sheep don’t say much about it when they reach the abbatoir.

But it was on the steepest part of the hill that the new transmission showed its colours. With a standard I-Shift and a fully loaded B-Double rig, the cab will buck and nod with chassis flex when the throttle shuts off 2,800Nm of torque and then bangs it on again when it’s meshed with a lower ratio.

Not so with the dual clutch option. The critical advantage is no loss of momentum on hills, and therefore no surge of fuel to recover lost speed.

Initially I let the gearbox make its way seamlessly to sixth gear, but then locked it in manual for the rest of the climb. I wanted to avoid the range change, which would likely cost me too much momentum. At points where the climb eased off, I just backed off the thottle to keep it below 1,800rpm.

At the top of Cunningham's, drivers would know there’s a final steeper section with a tight left hand turn. I clicked it back to fifth for that bit and then slid the selector back into auto mode as the rig rumbled over the crest.

If I owned one of these and operated it myself, I’d be using manual mode quite a lot. The up/down button falls directly under your thumb on the selector lever, and the new system means you get an instant effect when you want a different gear.

However the benefit is not just on steep inclines in the lower gears. At cruising speeds it’s so much easier to drop a cog at any time without having to pick your moment carefully.

I asked Volvo’s Fuel Efficiency manager Matt Wood why the company had gone the route of the enhanced AMT rather than a full automatic.

Matt acknowledged that a faster shift was of particular value in certain operations, such as liquids and livestock, where frequent full-throttle manual gear changes can spark big movements in weight distribution. But he noted that the new option placed the I-Shift with dual clutch with a significant price advantage over an Allison.

Volvo’s 13-litre is the smooth and silent type, and when combined with this new option only enhances the fuss-free, get-on-with-it approach to transport that Volvo’s FH delivers.

There's another bonus. You could probably do a 16-litre job with this 13-litre engine matched to the dual clutch option.

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