Volvo Trucks North America first introduced its I-Shift automated manual transmission (AMT) to the U.S. market in 2007. Built off a European model designed by its parent company, Sweden's AB Volvo, the I-Shift is a 12-spd., single-countershaft transmission built up with a splitter, a main section with three forward gears and one reverse gear, as well as a range gear. It does not use synchronizers in its main section and the “two-pedal” unit doesn't require a clutch pedal.
The I-Shift, which weighs between 597 and 610 lbs., is offered in three different versions to handle all power and torque inputs from Volvo's new engine family — made up of the D-11, D-13, and D-16 models. The transmission is an option on all of Volvo's truck models.
The I-Shift is programmed with Volvo's engine efficiency map for each engine rating. It works with special road sensors to continuously calculate the vehicle's speed, acceleration, torque demand, weight, rolling and air resistance, and road grade in 30-sec. intervals to optimize engine performance and fuel. A special feature is a system called Eco-Roll, which automatically disengages the engine when the vehicle is in top gear on long, slight downgrades that require no engine torque input. By allowing the engine to idle in these situations, Eco-Roll can reduce parasitic losses by as much as 30 hp. and thus conserve fuel.
Another new feature is Eco-Torque, which boosts the amount of torque available so the AMT doesn't have to downshift in hilly driving conditions, thereby helping maintain vehicle speed and fuel economy at the same time. For example, a Volvo 2010-compliant VN780 highway tractor equipped with a 435 hp. D-13 engine producing 1,550 lbs.-ft. of torque morphs briefly into a 500-plus hp. engine generating 1,750 lbs.-ft. of torque — all without any action required by the driver.
Altogether, Volvo offers up to eight rating “boosts” within its engine family, says Ed Saxman, Volvo Trucks North America powertrain product manager. Saxman points out that Mack Trucks Inc., Volvo's sister company, also offers similar Eco-Torque functionality with its mDrive AMT (based on the I-Shift) in conjunction with Mack's Econodyne engine line.
Offered on the Pinnacle with Mack MP7 and MP8 engines, the two-pedal mDrive automated gearbox not only improves driveability and driver satisfaction, but should also deliver up to a 1.5% improvement in fuel economy compared to a fully automated version, notes David McKenna, Mack's powertrain sales and marketing manager.
