Allison to go 10 speed

After being shown in the USA last year, the new Allison TC 10 gearbox received a lot of attention due to its smooth changing and fuel saving potential. At a recent demonstration event for all Allison transmissions, held in Queensland, top management of the US transmission manufacturer revealed the gearbox is on its way to Australia in the next couple of years.

The new transmission is a major departure for Allison. In the past, the company has concentrated purely on automatic transmissions and refining its torque converter, ratios and electronic control systems to get the best out of the driveline. Still using these wet clutch technologies, Allison has combined a 10 speed twin countershaft mechanical gearbox with its tried and trusted torque converter.

Production of the new transmission is due to commence in October in the US and we can expect some examples to start turning up on our shores sometime in 2013. The gearbox is aimed at the prime mover market, both intrastate and interstate. It should enable operators to set up trucks with low rpm at high speeds without compromising startability at the lower end of the box.

“We have targeted the TC 10 for the short haul truck market where there is a combination of city activity, start/stop, as well as highway driving,” said Allison CEO Lawrence Dewey, on his recent visit to Queensland. “That was one of the keys to the twin countershaft architecture, to make sure we were competitive with the mechanical transmissions in that part of the duty cycle as well as maintaining fuel efficiency in start/stop work. I would say, with the performance we’ve seen, that while we did not target the long haul market, I would not be surprised if a few of them end up in those applications.”

Over the past 10 to 15 years, perceptions about automatic and automated transmissions have changed beyond recognition. In the 1990s, manual transmissions were ubiquitous in the highway prime mover market and all the way down to light duty delivery trucks. There was a place for automatic transmissions in specific applications like concrete agitator, refuse collection and other vocational work. The autos used then were regarded as both heavy and expensive.

It was the introduction of the automated manual transmission, first of all in Europe and later through Eaton in the US, which began to change people’s perceptions of what automation could do for the trucking industry. Led by the Iveco Eurotronic and closely followed by the ZF AS Tronic and Volvo I shift, the Europeans came up with smooth shifting automatically actuated transmissions with fast electronically controlled clutch systems. This was followed by the Eaton Autoshift in the North American market and, more recently, the Eaton Ultrashift Plus.

Electronic control enabled smooth and swift gear changes, and ever improving software with effective communication with other vehicle systems meant the new gearboxes could replicate, to a certain extent, the performance of a better than average driver. Not only were AMTs sold as an alternative to manual gearboxes, but also as a substitute for automatic gearboxes.

The fast rise of the AMT stimulated a fast rate of development by automatic gearbox makers like Allison. The precise electronic control and ready communication with the rest of the vehicle systems, especially where multiplexed electrical wiring is fitted, was also available to the new automatic gearboxes. The latest iteration of automatic transmissions from Allison have been characterised by very good responsiveness to driver inputs and the inclusion of a number of electronic smarts to improve on road performance.

Another factor in the fast development of new product from Allison has been its change of ownership. Until 2007 the company had been owned by General Motors for 78 years. General Motors’ financial strife saw the Allison arm sold to investors Carlyle Group and Onyx Corporation. They put up considerable research and development funds. This increase in investment has been followed by Allison being floated on the New York stock exchange in March, freeing up further funds for future technology development.

With this new level of technology available to the company, it would appear Allison has realised the ability to extend the reach of its transmissions. The company has long been a staple in most US trucks working in an urban environment. However, the US, just like Australia, has held onto the belief in the Eaton Roadranger as the standard transmission in long haul highway trucks. The introduction of the new 10 speed from Allison shows a company confident with its new technology, attacking its competitors’ heartland.

The new TC 10 from Allison is a new type of gearbox. The torque converter is used only for initial takeoff, the rest of the changes are made without an interruption in power by the twin countershaft 10 speed box. Allison describes the system as ‘blended architecture’ with the transmission using the hydraulically actuated clutches used in automatic transmissions, making the changes from gears 1 to 10.

The basic gearbox has five speeds plus a two speed range changer. By using a twin countershaft design the transmission engages gears one, three, five, seven and nine on one countshaft and gears two, four, six, eight and ten on the other. When one gear is engaged the next gear up is already engaged on the other shaft and the clutch system swaps power across to the second countershaft when the change is made. Allison describes the process of making a ratio change as involving a slight reduction of power during shifts, to cushion them.

“The power rating of the TC 10 is up to 600hp and it is going to launch at 1650 ft lb of torque, but we will probably grow that to 1850 ft lb,” said Steve Spurlin, Allison Executive Director Global Application Engineering and Vehicle Integration, at the Queensland demonstration. “It’s a five on five gearbox, a five-speed section with two ranges. It has a low first gear ratio of 7.4:1 and has a single overdrive. It uses helical gearing to keep the noise consistent with our current automatic products. It will be using our fifth generation electronic control system. For the first time, the transmission control module is going to be mounted on the side of the transmission. Our weight target for the gearbox is 999lb (453kg).”

When being compared to its competitors, the new transmission comes in at around the same weight as the Eaton Ultrashift. The design means that torque can be applied through the driveline continuously through up and down changes. This means faster ratio changes and lower fuel consumption as there are no power interruptions during acceleration. It also means the engine brake can apply torque continuously as the truck downshifts while slowing down.

Allison also points out that its design means there are smaller gaps between the ratios, even on a 10 speed box, when compared to its AMT equivalent. Each ratio is about 17 per cent apart compared with percentages in the high twenties on many AMTs. The use of a torque converter means the ratio used for the first gear can be taller than is normal on a manual box. The way the torque converter brings the power in gradually, while protecting the driveline, makes it possible for the truck to set off in this higher ratio.

The combination of small steps between gears and the ability to keep the power on during changes makes for better control of fuel consumption. Engine rpm levels can be kept within a tighter band, closer to the sweet spot. This should mean the engine spends more of its time running as close to its optimum engine speed as possible.

Allison also claims the small ratio steps mean it is possible to set the vehicle up with a very low rpm level at top speed in top gear. The company says that because a quick down change to ninth gear can be made without power interruption, it is possible to maintain highway speed slipping quickly between ninth and tenth so speed, torque and power are maintained.

Allison also claims its testing has demonstrated a clear fuel consumption advantage of its gearbox design over its two main competitors on the US market. When the transmission is eventually launched in the US, a clear picture of how much these real-world savings represent can be more accurately assessed.

“We are currently running around 55 prototypes with the new transmission and we are tracking their results as we go along,” said Mr Dewey. “We will continue to work through the remainder of this year and finalise the design. In the segment we are targeting we only have about 3 per cent market share in the US. This is really new for us, it’s not designed to respond to the AMT, it’s designed to create new opportunity for Allison.”

This latest development should be with us some time next year and will face the usual assessment by operators interested in the new idea. Consistency and durability will be the attributes Australian buyers look for. If this transmission can deliver real fuel savings and ease of use, we may start to see it appearing in a number of truck brands.

The rivalry which has built up between transmission suppliers since the introduction of AMTs has genuinely seen a quantum leap in gearbox sophistication and quality which looks set to continue an improved driving experience and better fuel economy into the future.

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