TOWING WITH AN AUTO

Let’s look at the effects towing has on a vehicle with automatic transmission

WORDS AND PHOTOGRAPHY BY GRANT HANAN ADDITIONAL PHOTOGRAPHY BY CARAVAN & MOTORHOME

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When it comes to towing there is no doubt driving a vehicle with an automatic transmission is far more relaxing when compared to a vehicle with a manual gearbox, but how does this extra load affect the transmission? In this article, we explore transmission performance and what you can do to extend the life of your vehicle’s transmission.

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AUTOMATIC VS. MANUAL

What are the pros and cons of each when it comes to towing?

  • When towing, the auto has the advantage due mainly to the function of the Torque Convertor (TC). Basically the TC is a fluid coupling that multiplies torque and provides input to the transmission similar to riding the clutch in a manual. This function absorbs driveline shock and provides excellent control under high loads and low speed, particularly on take-off, up hills and situations that require precise vehicle control.

  • Modern Torque Convertors have a lock-up clutch that is applied to stop this slippage and offer direct drive similar to a manual clutch.

  • The only real downside is the amount of heat it can generate, but that can be addressed and in some vehicles the manufacturer’s software will not hold gear as desired.

  • A manual is harder to control precisely and requires more finesse under load and when hill starting, however a manual does have good engine braking capabilities and can be held in the selected gear, this can sometimes make the overdrive gears fragile.

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    WHAT GEAR IS BEST FOR TOWING?

    STU KITTO – WHOLESALE AUTOMATIC TRANSMISSIONS

  • Generally if the transmission will stay in a high gear, it will be fine to tow in that gear, if it constantly downshifts then it is best to select the lower gear.

  • When it comes to fuel consumption, higher gears and lower revs do not always result in better economy. When towing heavy loads, selecting a lower gear will increase revs and usually have minimal impact on economy, especially if you can control the lock-up clutch application in the torque convertor. We have developed a control unit for this exact purpose.

  • Lower gear/higher revs is safer at high speed and provides greater control and engine braking, an overdriven gear provides a feeling of being pushed and can be dangerous if evasive action is required at speed.

  • Lower Gear / higher revs also reduces load and consequently less heat generation in both engine and automatic transmission.

  • The key to transmission longevity is to reduce heat generation, either through driving technique, lock-up control or both.

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MODERN AUTO ADVANTAGES

Generally speaking most modern autos are being released with more gears; for example the Jeep Grand Cherokee has an 8 speed transmission. The more reduction gears there are available means better take off ability with a van in tow, more low speed control, better engine braking and less heat generation. All of these points address any negative traits that automatic transmissions may have had in the past and is a clear reflection of how technology is assisting in contributing to safety through gear selection and lock-up control under all driving conditions. Modern control units have software that can monitor all conditions and select the ideal gear to provide maximum performance and safety and making the towing experience easier and safer for all involved.

Having a sequential option to downshift and control engine speed during decent is a modern option that will also stop downshifting at too high an engine speed and avoids compression lock.

COMMON MISTAKES WHEN TOWING WITH AN AUTOMATIC

Probably the most common mistake when towing is the misconception that driving conservatively in the drive position reduces fuel consumption and load. Most automatics will not select lock-up of the torque convertor when towing in the drive position and will constantly shift in and out of lock-up and even down change to a lower gear. Driving in the drive position when under load will contribute to high heat generation in the transmission and overheating in many cases. It is generally better to select the lower gear to control heat and increase reliability.

SERVICING

It goes without saying that regular vehicle maintenance and servicing will pay dividends. When getting your automatic transmission vehicle serviced, Stuart made these suggestions.

  • Ensure the technician is confident when it comes to transmission knowledge. Many mechanics will not touch an automatic transmission (and for good reason). If they do not have the knowledge and the technical back up then it is best left to a specialist.
  • A thorough road test is the key to understanding the operation and only a specialist may notice something both yourself and a mechanic may not.
  • Fluid condition and evidence of contamination in the pan and filter can be used with the road test to provide an accurate assessment of condition. Of course quality replacement parts and correct fluid type are essential.

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EXTENDING TRANSMISSION LIFE

CHECK THE FLUID

If your transmission has a dipstick, use it to check the fluid amount, colour and smell. Checking sealed units can only be performed by a specialist.

ATTEND TO PROBLEMS IMMEDIATELY

Small things left unattended could turn into a major breakdown, so don’t overlook or disregard them. eg. a small fluid leak, noisy shifting, or hard selection.

INSTALL A TRANS COOLER

Keeps the fluid cooler and helps to eliminate excessive heat, particularly as everything works harder when towing.

INSTALL AN INLINE FILTER

Although the transmission will have filters inside, adding an external inline filter allows easier access for frequent changing.

SERVICE REGULARLY

An annual fluid and filter change can add years to your transmission’s life.

CORRECT FLUID

Use the correct fluid for your type of transmission (refer to the owner’s manual). There are many brands and types of fluid on the market, but they are not all the same. Use the wrong fluid specification and you could be damaging your transmission.

TRANSMISSION SHIFT

Observe your driving style and assist transmission shifting by backing off slightly just before the shift change. This will minimise the transmission load and assist with a smooth change.

VEHICLE SERVICING

Keeping the vehicle in tip top condition will reduce strain and any unnecessary stress on the drive train and transmission. Ensure the engine is regularly tuned, maintain the cooling system, run good tyres with correct pressures, and include suspension servicing.

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RECOMMENDED UPGRADES FOR TOWING

  • Lock-up control kit to hold lock-up on, control temperature and increase fuel economy.

  • Full Synthetic ATF / nomad valve body upgrade to enhance shift quality, reduce heat generation and increase performance.

  • Transmission fluid temp gauge, to read LIVE temperature.

  • Automatic transmission reliability and performance is directly related to fluid temperature monitoring and control.

    SUMMING UP

    When it comes to towing an RV, today’s automatics offer great performance and ease of operation. A properly looked after transmission with regular servicing and maintenance should have an extended life. At the end of the day, choosing to drive an automatic is a decision of personal preference, but one that is ever increasing in popularity.

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