ZF’s AS-Tronic has successfully dominated the automated manual transmission market for two decades. Now it’s time to welcome its successor, the ZF TraXon. – Words by Chris Mullett.
With 20 years of manufacturing the AS-Tronic AMT under its belt, German transmission manufacturer, ZF, has notched up sales of over one million units since its launch in 1997.
The development work for the AS-Tronic was carried out with a view to the first implementation being for IVECO. But it soon became obvious to the other main European truck makers that the innovative technology in ZF’s gearbox was going to be a game-changer, adding to its desirability and acceptance by operators worldwide.
The second generation of the AS-Tronic launched in 2000 created a range of transmissions capable of handling torque outputs from 500 Nm through to a peak of 3100 Nm, with a choice of 12-speed or 16-speed alternatives, dependent on the specific vehicle application. Rather than offering a driver controlled gear preselection as offered in the early versions, the new fully automated logic introduced with the second generation units immediately simplified the shift protocol and ratio selection.
The addition of the Intarder, ZF’s transmission brake, provided operators with a fully integrated retardation system that boosted engine braking power, while at the same time reducing service brake workload and brake or pad lining wear by up to 90 percent. The clever logic incorporated between the CAN bus electronic interconnectivity improved reaction times for shift changes, at the same time reducing driveline stress and thereby improving durability and safety.
At the 2012 IAA Commercial Vehicle Show event in Hanover, ZF and IVECO signed a letter of intent related to the fitment of the TraXon transmission family in products such as the Stralis and Trakker models.
In March 2015, ZF announced the global availability of the TraXon modular automatic transmission system, after the expansion of its operating field trials to incorporate additional manufacturers such as MAN and DAF, which joined IVECO to provide an alternative to the latest generation I-Shift from Volvo, the mDRIVE from MACK and the Opticruise from Scania.
As the first major truck manufacturer to offer the ZF TraXon transmission in the Australian market, MAN, with its recently released TGX D38, has taken a step ahead of its competition by offering the 12-speed TraXon transmission, which it refers to as the Tipmatic2.
This unit incorporates three new fuel saving modes, idle speed driving from 600 rpm on release of the brake pedal but without throttle pedal depression and Efficient Roll, plus Speedshifting, which shortens the required time for gear splits between 10th, 11th and 12th ratios. This speeds up the gearshift timing on inclines to reduce fuel use and maintain momentum.
Also included in the TraXon spec is the PreVision GPS linked cruise control gearshift optimisation that MAN refers to as MAN EfficientCruise.
By linking the TraXon transmission to the 560 hp, 15-litre six-cylinder Euro 6 D38 engine, the new ZF starts its life Down Under with an ideal match, benefiting the operator from a torque output that runs from 930 to 1350 rpm, with two-stage sequential turbocharging. Maximum power is 560 hp with peak torque of 2700 Nm.
What makes the TraXon substantially different from some of its competitors was the decision to develop the new transmission as a modular system incorporating five different elements.
The basic architecture of the automated manual transmission allows for torque ranges in direct drive up to 2800 Nm, and in overdrive up to 3500 Nm, aimed at applications such as the medium to heavy vehicle gross weight segment.
TraXon can be driven by a single or dual-disc dry clutch or include a torque converter clutch.
For higher weight application involving high gross weight prime movers or mobile cranes with multiple axles, the ZF TraXon torque converter module combines with the TraXon transmission and the ZF PowerDivide modules to introduce a torque converter clutch that couples to the basic transmission.
The optional hybrid module contains a 120 kW/1000 Nm electric motor/generator combined with an automated separating clutch. This enables hybrid functions such as recuperation, electric driving, a boost function for increasing performance, an electric stop/start function, and the possibility of electric PTOs. The hybrid feature can also be used to power auxiliary applications such as cooling and driver compartment functions, even when the vehicle’s primary engine is switched off.
In the development of the system, studies into the effectiveness of hybrid use in heavy-duty transport have found that fuel savings of five percent are possible under city driving conditions.
A more traditional engine-dependent PTO module is also available, which can service a multitude of applications with torque of up to 2000 Nm. This is installed between the engine and transmission and is ideal for auxiliary features that require high torque, for example cement mixers, fire trucks and mobile cranes.
In the general transport sector where torque outputs are for up to 3500 Nm, TraXon features an anticipatory shifting strategy through the incorporation of PreVision GPS, which provides a link to the transmission with GPS data and digital mapping. In this way, unnecessary gearshifts can be avoided as the combined control system “foresees” the gradient change ahead or an oncoming sharp turn and can determine whether to avoid an unnecessary upshift or downshift by holding onto the selected ratio.
Dependent on the intended application, TraXon is available in 12 and 16-speed models, with both available in direct or overdrive versions, with the overdrive featuring a particularly long top ratio that provides significant reductions in engine speed whilst in top gear.
For a traditional automatic transmission, this would drastically increase the shift frequency, especially when dealing with slight uphill gradients. With the dual-clutch module, it is possible to perform these downshifts and upshifts, under load and without torque interruption, optimising fuel use.
Because the twin-clutch module allows the next gear ratio to be preselected, with a 200-millisecond clutch engagement, rapid downshifts without torque interruption are possible on gradients, making for faster journey times. The TraXon twin-clutch module is seen as being at the cutting edge of a future trend in truck transmissions. It should be noted, however, that the twin-clutch module is not currently available for the Australian market.
The TraXon modular system also includes an optional torque converter clutch for use in heavy-duty prime mover applications. The system lowers life cycle costs with wear-free use at high-input torques.
With a claimed efficiency of 99.7 percent from direct 1:1 ratio top gear versions, there’s also a claimed reduction in noise of 6.0 dB over the previous AS-Tronic while offering a wider ratio spread. This gain was achieved by integrating a new anti-rattling damper alongside the new gearing design, and innovations in the transmission housing.
Two reverse gears are standard, but a four reverse gears option is available. The justification for four reverse gears is based on the need to manoeuvre high gross weights at low speeds, with the standard transmission ratio suited for normal on-highway work and the optional four reverse gears set ideal for slow, precise manoeuvring. Where higher speeds are required, the four reverse gears enable higher transfer speeds such as might be required at highway construction sites.
The TraXon Smart software brings the truck operator systems that are becoming a more common feature on prestige and luxury cars. Systems such as ECO or high performance with the Power programme enable the driving strategy and shift dynamics to be changed to suit the operating environment. This function occurs either via a manual over-ride by the driver or by enabling the software to make the programme changes automatically.
Stop/start systems have been adopted by the car and light commercial vehicle industry, but TraXon brings this technology into the realms of the heavy truck, shutting down the engine during prolonged traffic delays and then providing a quick start solution when the traffic ahead starts to move.
The rolling function, similar to other systems such as ECO-Roll, activates the gear shifting logic into selecting neutral, optimising fuel consumption and minimising drag losses when not travelling under high engine loads. When combined with PreVision GPS, the rolling function is able to recognise differences in topography in advance and adapt the driving strategy accordingly.
Applications on difficult terrain are always a challenge – for driver and vehicle. The rock-free function has an extended clutch control that is able to free the vehicle from in-ground depressions and other obstacles by invoking a rocking movement.
The PowerTorque team reported first on TraXon when it was released to European eyes at the 2014 IAA Show in Hanover. For real-time performance and evaluation, check out our first road test impressions of the full Australian spec TGX D38 on pages 12-15 in this issue.