The trend toward automatic transmissions – what does it mean for the lubricant?

by Darryl Purificati, Sr. Technical Advisor, OEM/Automotive at HollyFrontier Lubricants & Specialties, which includes the Petro-Canada Lubricants brand

There are currently three different transmissions commonly available for the heavy-duty fleet sector – automatic, automated manual and manual. In North America, automation rates are estimated to have increased from approximately 70 percent to 95 percent in the past 10 years. According to Allison Transmission, a manufacturer of fully automatic transmissions for medium- and heavy-duty commercial vehicles, this uptake could be attributed to fleets finding that automatic transmissions are easier and less costly to maintain, resulting in a lower lifetime cost as well as improved vehicle uptime.

The transition to automation

The ongoing journey for improved fuel economy and the evolution of alternative fuels have been key drivers for medium and heavy-duty fleets as they transition toward automatic transmissions.

Automated manual transmissions (AMTs) are primarily known for improving fuel economy, but they also have the added benefit of reducing maintenance costs. AMTs require fewer clutch repairs compared to North American Council for Freight Efficiency has also found that fleets are realizing a 1 – 3 percent improvement in fuel economy by using AMTs over manual gearboxes

Comparatively, a 2015 study by Frost & Sullivan found that automatic transmissions can improve fuel economy by 3 – 5 percent.  Alongside fuel economy benefits, both AMT ‘and automatic transmissions enable drivers to have greater focus on the road rather gear shifting, which can help reduce driver fatigue.

While there is an initial lower cost for manual transmissions meaning they can be a cost-effective option for fleets with experienced drivers, automatic or automated manual transmissions significantly reduce the impact of driver behaviour. When total lifetime cost of training, maintenance and fuel consumption are taken into account, automatic and automated manual transmissions can offer a cost-effective solution.

 The transmission’s impact on lubricants

Automatic, automated manual and manual transmissions have specific hardware architecture that will require for example, different friction modifiers, different levels and types of anti-wear additives and corrosion protection additives for the hardware’s soft-yellow metals.

Each transmission fluid is formulated to optimize the performance of the friction plates or clutches and to be compatible with the transmission’s seal materials. Corrosion protection, as well as foaming and aeration control, are also important characteristics of transmission fluids.

Transmission fluids are often required to meet specific criteria set out by the Original Manufacturer Equipment (OEM), which enables the lubricant and transmission to work together for optimal performance and durability, as well as superior protection of the transmission hardware.

For this reason, it’s crucial that operators use the correct fluid in the correct transmission and for their specific application. Operators should always follow OEM recommendations when making a transmission fluid choice to help protect and maintain, where relevant, the OEM warranty.

A closer look at automatic transmission fluids

Transmission fluids are formulated differently depending on the hardware requirements; there are fluids for manual transmissions, automated manual and automatic transmissions. Automatic transmission fluids provide the required lubrication, cooling and viscosity at low and high temperatures, while maintaining optimum and stable clutch-friction performance through the life of the fluid. These fill-for-life fluids are designed with excellent oxidation resistance and shear stability to provide adequate hardware protection.

The shift to automatic transmissions has resulted in innovation in the formulation and lubricant technology of transmission fluids. DuraDrive HD Synthetic 668 is specially formulated for Allison Transmission’s TES 668™ specification and provides greater anti-shudder durability, improved oxidation control and optimal wear protection.

Through reduced wear and unplanned maintenance, DuraDrive HD Synthetic 668 contributes to a smoother operation and enhanced performance which results in a lower total cost of ownership. The automatic transmission fluid is specified for on-highway vehicles, including vocational applications, and is fully backward compatible for all 1000-4000 Series and H 40/50 EP and eGen Flex hybrid Allison transmissions that previously required an approved TES 295® fluid.

The shift to automation in transmission technology over the last 10 years has resulted in improved fuel economy and reduced maintenance costs for the heavy-duty fleet sector. Acting as a catalyst for the development of innovative transmission fluids with lower viscosity properties, today, fleets can benefit from fuel economy gains from both their transmission and transmission fluid, as well as superior lubrication protection and performance.

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