Picking the right transmission mode

Expert advice on things to consider when choosing transmission for commercial vehicles

Picking the right transmission mode
Isuzu Australia chief engineer of product strategy Simon Humphries.


Picking a transmission for your truck is not an easy task not simply because of the choice between three options – manual, automatic and automated manual transmission (AMT) – but because everyone, from drivers to fleet operators to procurement officers, has an opinion and a personal preference.

Isuzu Australia chief engineer of product strategy Simon Humphries attempts to simplify the choice by highlighting a few things to consider when selecting your truck transmission such as fuel economy, productivity, traction, roll-back and the job type.

While fuel economy is dependent on driver behaviour and road experience, particularly when it comes to manual transmission; however, a case study undertaken by the Green Truck Partnership, out of the Roads and Maritime Services (RMS) in NSW, revealed better results with AMT.

The study "revealed that Automated Manual Transmissions (AMT) delivered a fuel efficiency benefit in the order of 11 per cent compared with a fully automatic transmission – during field testing," Humphries says.

He says when it comes to productivity automatic transmissions are a better option, especially when operating in urban environments that have more traffic stoppages.

"As any long-haul driver will attest, every time you make a shift in a manual transmission, you briefly take your foot off the throttle and lose some momentum.

"The total time lost starts to add-up very quickly.

"Allison Transmission claims the powered shift of an automatic transmission gains anywhere from four to seven seconds every 400 metres travelled."

He argues that, in most cases, automatic transmissions allow "greater flexibility, manoeuvrability, traction and gradability (the steepest grade a truck can climb with a full load) on less-than-favourable terrain or gradients.

"They provide continuous power and torque to the wheels, meaning critical power to the drive-wheels isn’t interrupted when it’s needed most.

"Specifying an automatic or AMT with a torque converter will help your drivers, especially those with less experience, negotiate these sorts of loads more safely and effectively."

Humphries suggests undertaking a detailed cost analysis including initial setup and future servicing costs to understand which transmission suits your business needs.

Another important factor to consider is the work type.

"From small parcel delivery through to ‘out of gauge’ loads, the size and weight of road tasks vary considerably, so not only do your driveline specs need to be spot on, your choice of transmission must also match the task at hand."



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