Technology comes full circle - Volvo Truck gearbox
The advanced gearbox of today has reverted to what it was back in 1928 – three-speed and non-synchromesh - at least, that is the way it is for Volvo Trucks. The development span between that first gearbox and the very latest – the I-Shift – encompasses a huge amount of work and many landmark accomplishments.
1928 saw the very first Volvo truck leave the factory. It was a very popular vehicle – in fact far more popular than its passenger car ancestor the ÖV4, whose driveline components were carried over into the truck in their entirety. This first truck, known simply as the Volvo Truck Series 1, produced 28 horsepower and had a three-speed non-synchromesh gearbox.
It was not until 1931 that Volvo built its first trucks without using driveline components from the company’s passenger cars. The gearbox in the new truck series was a robust four-speed unit specially designed for heavy vehicles. The new trucks also had sturdy rear axles with a reduction gear.
In these non-synchromesh gearboxes, it was necessary to press the clutch twice to change gears. This heavy double-declutching and shifting of gears solely by manual force put considerable physical strain on the driver. That is why it was hailed as an important leap ahead when synchromesh gearboxes appeared on the market in the 1950s.
“They marked an immense improvement in the driver’s working conditions: from a job requiring special training for gear changing to became more like driving a passenger car,” says Åke Zander, technical director at Volvo Powertrain and the person responsible for drivelines and hybrids.
During the 1950s, Volvo also started experimenting with automatic transmissions. However, it would take another 40 years for automated transmission to finally make its breakthrough. Before that, auxiliary gears such as range-change and splitter transmissions made their entry into the truck cab.
However, auxiliary gears were really only a natural part of the development process and did not mark a major leap ahead. At least that is the view of Mart Mägi, a former professor of automotive technology at the Chalmers University of Technology of Gothenburg in Sweden.
“From a technological development perspective, the inclusion of additional mechanical gears behind and in front of the base gearbox was only a minor step in overall progress. The first truly revolutionary concept was the gearbox itself, which entered into use just over a century ago. The next significant technological advance was synchromesh, followed by automation,” explains Mägi.
“The development of automatic transmissions for trucks progressed very slowly. However, once they arrived they were little short of epoch-making,” says Mägi.
Volvo Trucks’ first automatic transmission – the Powertronic – arrived in 1992. Nine years later, Volvo took another decisive technological leap ahead with the introduction of the first generation of the I-Shift automated transmission. Today this transmission is the jewel in Volvo Trucks’ crown and has won widespread customer recognition as an industry leader in this field.
Åke Zander relates that it was only with the advent of the I-Shift that customers finally started appreciating automated transmissions.
“Volvo has always had a strong selling point with its gearboxes, but when the I-Shift arrived in 2001, it received a particularly warm welcome. The I-Shift brought increased functionality, reliability, driveability and fuel efficiency - something that was entirely new on the market,” he explains.
The I-Shift is a splitter and range-change gearbox with three non-synchromesh gears in the main gearbox. With its splitter and range ratios, the transmission has a total of twelve forward gears, which are engaged and synchronised entirely electronically. The I-Shift communicates with the engine. For instance, it activates engine braking (the VEB - Volvo Engine Brake) as necessary, slowing down the engine and optimising each gear change in a way that no driver with a manual gearbox can replicate.
The latest generation of the I-Shift was introduced in 2009 with the launch of Euro-5. Using a variety of software updates, it is optimised for various operating conditions, from highway to construction site. Today, more than 70 per cent of all new Volvo FH and FM trucks sold are fitted with the I-Shift.
With this gearbox, the wheel comes full circle and Volvo has completed the journey from a three-speed non-synchromesh gearbox to the I-Shift, in which the mechanical heart of the unit is also a non-synchromesh three-speed gearbox.
However, Mägi prefers to look ahead beyond the I-Shift, when he says, “In the future, the entire conventional gearbox may become obsolete – for instance in series hybrids, if or when we get a properly functioning hybrid system in trucks too. The next big step ahead is hybridisation and that is already on its way.”
Electric power transmission does not require any gears at all in the way they are used in today’s gearboxes. Computers take over control of power delivery from the engine to the driven wheels via intermediate electric motors and battery packs.
Zander agrees that hybrids are set to be the next major development step, but predicts that the gearbox is still going to be around for some time yet.
“It will be needed together with an electric motor. Most of Volvo Trucks’ products are too heavy for electric power alone – the electric motor and batteries would be too big and expensive. And it is always customer benefit that determines when and if a technological paradigm shift is viable. Volvo Trucks’ hybrid trucks today are equipped with the I-Shift,” he says.
