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A deep dive into transmissions

Automatic transmissions play a crucial role in the modern vehicle, enabling smooth gear shifts and optimal engine performance. Despite manufacturers’ claims of ‘fill for life’ transmissions, this article aims to shed light on the necessity of regular servicing, especially for individuals engaging in city driving and towing caravans. Additionally, we will explore the impact of high outside and working temperatures on automatic transmissions, unravelling the complexities of maintaining these intricate systems.

The Myth of ‘fill for life’

Numerous car manufacturers promote their automatic transmissions as “fill for life,” implying that these systems require no maintenance throughout the vehicle’s lifespan. However, this assertion often neglects the real-world stresses that transmissions encounter, particularly in challenging conditions like city driving and towing.

City driving and transmission stress

City driving, characterised by frequent stops, starts, and short trips, subjects the transmission to increased stress and heat generation. Over time, this elevated temperature can lead to the breakdown of transmission fluid, resulting in decreased lubrication effectiveness and potential damage to internal components. Regular servicing is essential to flush out deteriorated fluid and replace it with fresh, high-quality lubricant, ensuring the transmission’s longevity and optimal performance.

Image: Supplied by IAME

Towing caravans and transmission wear

Towing caravans places an additional burden on the transmission, as it grapples with the extra weight and strain imposed by the towing process. The increased load translates to higher transmission temperatures, accelerating fluid degradation. In this scenario, regular servicing becomes paramount to prevent overheating, ensure proper lubrication, and maintain the transmission’s overall health and durability.

Understanding the specific challenges posed by towing activities allows vehicle owners to appreciate the importance of proactive transmission maintenance in preserving the functionality of these intricate systems.

The impact of high temperatures

Automatic transmissions are highly susceptible to the adverse effects of high temperatures, originating from both the external environment and the heat generated during operation. Prolonged exposure to elevated temperatures can lead to fluid breakdown, increased friction, and accelerated wear on transmission components. Regular servicing plays a crucial role in mitigating these issues by replacing degraded fluid and ensuring the transmission operates within optimal temperature ranges.

Exploring the intricate relationship between temperature and transmission health provides valuable insights for vehicle owners, guiding them in adopting preventative measures to safeguard their vehicles’ crucial components.

Service Intervals and Best Practices

While some manufacturers propose extended service intervals, a more proactive approach is advisable, especially for those engaged in city driving and towing heavy loads. Regular servicing, including fluid changes and filter replacements, not only extends the life of the transmission but also enhances overall vehicle performance. Adopting best practices in transmission maintenance contributes to a safer and more enjoyable driving experience, ensuring the vehicle remains reliable and efficient. Understanding the nuances of service intervals and best practices empowers vehicle owners to take charge of their transmission’s health, reinforcing the importance of routine maintenance for long-term reliability.

In conclusion, the purported “fill for life” claims by some manufacturers may not fully encapsulate the nuanced demands placed on automatic transmissions, especially for individuals involved in city driving and towing caravans. The impact of high temperatures on transmission health further emphasises the need for regular servicing to maintain optimal performance.

By adhering to proactive service intervals and embracing best practices, vehicle owners can ensure their automatic transmissions remain reliable and efficient, contributing to a safer and more enjoyable driving experience. The intricacies of transmission maintenance underscore the importance of staying informed and proactive in preserving the longevity and functionality of these critical components in modern vehicles.

Image: khunkornStudio/

Extra Advice given for city driving and transmission stress:

Often vehicle manufactures will list in the vehicles owner’s manual, between what they consider when the vehicle is driven under normal conditions and or extreme/abnormal conditions. This can be considered with city driving and or in towing conditions.

In majority of cases this information can be obtained in two ways by reading and checking the vehicles owner’s manual or contacting your local automatic transmission specialist and asking for advice, as each circumstance can require slightly difference advice to be given.

So, this will or can influence if and when your automatic transmission requires servicing and or attention. By understanding this advice you can schedule a more precise servicing needs that your vehicle requires making it more reliable, safer and better in servicing your needs.

Extra advice given for towing caravans and transmission wear:

There are also other avenues that can be explored in helping when towing caravans to try and keep the possible issue of the transmission experiencing high temperatures and that is by fitting an external automatic transmission cooler, but making sure that an external cooler application is available for the prescribed vehicle that you have on hand.

In conjunction with this, driving the vehicle in a combination of “D” mode and manual mode so that once the vehicle is up to speed and cruising to the surrounding road conditions, so that the engine and transmission are not under extreme load or the engine rev range is not excessive or the engine/transmission is not hunting up or down, but the engine is purring nicely.

To achieve this state, it may mean that the automatic transmission is not running in its highest gear ratio.

For an example in a Y62 Nissan Patrol V8 with a 7-speed automatic transmission; the cruising gear that it can be mostly comfortable in, is in manual “5th” selection at a cruising speed of around 100km/h, with a possible rev range of around 2,000RPM.

This is only an example as the driving conditions can change and or the vehicle or the vehicle being towed, weight wise can vary. It sometimes can come down to, if there is a headwind or a tailwind being experienced at the time.

Image: SKT Studio/

Extra advice given for towing caravans and transmission wear continued:

Another area or item is when a Bullbar is fitted to the front of a 4WD, and the vehicle is going to be used especially for towing. When a Bullbar is fitted and because of its design it protrudes more forward of the front of the vehicle than the original bumper bar. Therefore, the gap between the rear bottom side of the Bullbar and the front of the radiator is quite extensive.

So, as the vehicle is driven, the normal amount of air hitting the front of the vehicle comes through the vehicle grill and if applicable, also through the air slots in the front of the Bullbar, but  then because of the extensive gap mentioned, the majority of air can take the least line of resistance after passing through the grill and is dumped down onto the road surface and then flows under the vehicle.

Then there is less air that continues through the radiator core reducing the performance of the normal cooling process compared to when it had a standard Bumper Bar fitted. To return to a similar correct amount of air flow that should be, install an underbody protection to the front of the vehicle, please see picture, from the rear of the Bullbar to the front Chassis rail.

Apart from protecting the engine sump area, the major effect it has is to act as a small dam which can then allow a similar amount of correct air being directed through the radiator keeping it to a similar cooling performance as if the vehicle still had the original Bumper bar fitted.

The referred picture is there as a strict reference as to the message that is trying to be conveyed and has no reference as to what manufacture is required to used.

Extra advice given for service intervals and best practices:

Most vehicles in Australia are classed as world cars as they are sold on the world stage. Australia can subject these vehicles to some conditions that are unique to this country so seeking advice from your local or closest transmission specialist about the automatic transmission in your vehicle would help in maintaining and keeping your vehicle in a reliable safe state.

As the vehicle and the transmission moves up in mileage a certain amount of wear particles, because of their micron size can be encapsulated within the transmission oil, so that as the oil is moving around within the transmission so are the wear particles which can over time add further wear and tear to the various components of the transmission.

This can shorten the overall life of the transmission. By changing most of the transmission oil on a regular basis, you are removing a range of these wear and tear particles.

In some front wheel drive or all-wheel drive vehicles the Automatic Transmission filter is incorporated inside the transmission, so, in this situation it would be impossible to change the filter when performing automatic transmission service, therefore changing the oil regularly becomes more beneficial to the longer life of the transmission.

Most vehicle manufacturers now specify and list a certain type of automatic transmission oil that suits their vehicles, so it is critical that the correct oil that is specified for your vehicle is used.

In most cases, it is strongly recommended using the original specified type genuine vehicle manufacture oil that they have listed for your vehicle.

At the time of this article being written, the author experienced the situation with the automatic transmission in his own vehicle, a, Holden Acadia 2019 with 49,000km where the transmission oil had changed to a very dark red to a black colour depending on the light source used.

The start of the oil colour change was noted around the 40,000km mark. Most of the mileage was a combination of stop- start city driving with some trips to and from Brisbane, Sydney, and Melbourne. This mileage driven aligned with the general rule within the industry that the transmission service intervals are performed between 40,000 to 60,000 km of mileage travelled. So, a transmission service was performed, changing as much oil as possible, and using oil purchased from the local genuine listed dealer. The transmission oil is now a clean bright red colour.

The maintaining a maintenance schedule over the life of your vehicle is the key to a safe and ongoing happy motoring.

Always stay safe and drive safely and keep abreast of what is happening around you.

  1. Smith, J., “Understanding Automatic Transmission Fluids,” Society of Automotive Engineers, 2010.
  2. Johnson, A., “The Impact of Towing on Vehicle Transmission Systems,” Journal of Automotive Engineering, 2015.
  3. Automotive Manufacturer’s Service Manuals and Recommendations.
  4. Brown, M., “Effects of High Temperatures on Transmission Performance,” International Journal of Mechanical Engineering, 2018.
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