Volvo Truck claims to be first in the world to launch a dual-clutch automated mechanical transmission in heavy trucks, and to this reporter’s knowledge, that is correct. Deliveries of the I-Shift Dual Clutch started in Europe this fall. There's no official word yet if they will be available in the U.S., but it's seen as likely by many in the industry.

The two Volvo I-Shifts are similar mechanically, but to the driver they operate much differently.

As a concept, dual clutch transmissions appeared in the 1980s in auto rallying and racing. Some European cars now offer them, and Eaton recently introduced a dual-clutch transmission for medium-duty trucks.

The current I-Shift automated manual, with a single clutch, goes back to 2002 in Europe and 2005 in the U.S. About 95% of Volvo's sales of heavy trucks in Europe last year included the I-Shift, and in the U.S. it's now in 74% of Volvo heavy trucks.

The two Volvo I-Shifts are similar mechanically, but to the driver they operate much differently.

I-Shift Dual Clutch can basically be described as two parallel connected gearboxes in one housing. One gearbox contains the even gears and the other has the uneven gears. When one gear is active, the next gear is pre-selected in the second unit. When shifting changes from the first gearbox, the other is poked in. This provides ratio changing without any disruption in power or speed.

The I-Shift Dual Clutch has two input shafts, one located inside the other, and the two clutches. This allows two gears to be engaged simultaneously. Which of the gears that is activated is determined by which clutch is engaged.

Volvo’s I-Shift Dual Clutch weighs 222 pounds more and is 4.72 inches longer than the single-clutch I-Shift.

Demanding driving

Volvo showed the I-Shift Dual Clutch to the European press corps recently in south-coastal Spain. We drove almost 300 kilometers (about 180 miles) using 12 vehicles. All were typical European 4x2 tractors with three-axle semi-trailers, loaded to 40 metric tons or 90,000 pounds GCW. Some were equipped with Dual Clutch I-Shifts, while others had the regular single-clutch I-Shift.

  The reason for choosing this part of Europe was the demanding, long and steep ascents and descents of up to 7 and 8 percent. One 65-kilometer (40-mile) leg started at sea level, rising to 916 meters (2,005 feet).

I became especially fond of a FH13-liter with 500-hp engine and 2500 Nm (1844 lb-ft) of torque equipped with the Dual Clutch. It took off almost like a bullet and changed gears fast and without any interruptions. One could only hear, not feel, most gear changes.

Like a regular I-Shift, the new transmission skips some gears whenever possible, and makes only one small pause, during a range shift between 6th and 7th gear. Gear changes were made at low rpms, but revs did not drop during gear shifting. Low engine speed gave an extra comfortable setting in an already quiet cab. Volvo says fuel consumption does not exceed a "normal" I-Shift.

In the long and steep downhills, the transmission shifted down more quickly and more often than otherwise, due to the activated engine brake and retarder. This is controlled by the cruise control, where the desired maximum speed is set. The Volvo cruise control switches are on the left side on the steering wheel, and prompting slower or faster set speeds is done with a superb thumb switch.

It is amazing how quickly one can lose previous frames of reference. After time in a truck with an I-Shift Dual Clutch, an otherwise distinguished and popular long-haul FH 13 with a 460-hp engine and a single-clutch I-Shift felt far weaker with its slower gear changes.