Before you begin: Please note these important safety considerations

As these Heat Testers will need to be applied to under-vehicle driveline components, please take the following into consideration to ensure you do so safely. Please ensure that:

  • You have appropriate Personal Protective Equipment (PPE) for cleaning the gearbox or axle casing and for Heat Tester application. 
  • The components that the Heat Tester(s) will be applied to and surrounding components (i.e. exhaust, radiator, brakes) have sufficiently cooled down to avoid any risk of skin burning. Leave sufficient time noting that transmission and brake components can take considerable time to cool down. 
  • When using a solvent to clean the sticker application area, ensure adequate ventilation and avoid direct skin contact.
  • You feel confident to apply the Heat Testers and are in a safe environment to move under the vehicle. If not, ask a trained mechanic to apply the Heat Testers in a suitable environment.
  • The engine is off and cannot be turned on or moved by another person (keys out of the ignition) to avoid risk of turning drive shafts or vehicle moving.
  • The vehicle is properly immobilised (i.e. using hand brake, engaging gear, wheel stop-blocks)
  • If the vehicle is jacked up or raised, ensure this is done securely so that there is no risk of the vehicle moving, falling off or being pushed off its supports.

If possible, apply the Heat Testers so that they can be visually inspected without having to go underneath the vehicle.

Usage instructions

The following Questions & Answers section is intended to give a basic user instruction of the Heat Tester. 

Q: What is this Heat Tester?

A: The Heat Tester is a specifically designed irreversible temperature sticker that will allow you to see the maximum temperature that your driveline components experience. 

Q:How can I read the Heat Tester:

A: The scale on the Heat Tester shows the maximum temperature it has reached by the scale indicators changing colour permanently.

Q: How do I use these Heat Testers?

A: These Heat Testers work by sticking them onto the driveline component (gearbox or axle) you want to measure. After applying and running a typical driving cycle of the vehicle (speed, load) the maximum temperature that the component is experiencing can be read. 

Q: Why do the gearbox and axle get hot?

A: The heat in your driveline is generated from energy from your engine that is not converted into moving the wheels. All heat in your driveline is caused by friction. This can be either friction from the gearbox itself or from resistance of circulating the oil. 

In order to reduce driveline heat, both types of friction should be minimised to ensure maximum driveline efficiency and protection of the driveline components from wear. 

Q: Where do I apply these Heat Testers?

Ideally, the Heat Testers should be applied:

  • On axles: on the lower half of the back cover 
  • On gearboxes: On any smooth section of casting or sump plate 

For successful application of the Heat Testers, do ensure that:

  • The contact surface is clean and smooth, with good contact of the heat range to the casing, preferably not crossing a gasket. In most cases the surface will need to be cleaned and de-greased before applying the sticker.
  • It is not in a position where the Heat Tester would accumulate dirt or would be hit by stone chippings 
  • There is no radiating heat from exhaust components or brakes, and not directly in an air stream from a radiator fan as this may influence the measurement. In case of compact driveline component packaging, ensure the Heat Tester is not heated up in a confined space.
  • The driveline component being measured is not completely thermally connected on to a thermostat-controlled unit (i.e. a gearbox bolted to the engine) or itself equipped with a thermostat-controlled oil cooler, as this the Heat Tester will only verify the correct working of the gearbox / axle cooling system.
  • If possible, the Heat Tester is put on a lower part of the component is best as the oil sits low and holds most of the heat.

Q: What will the reading tell me?

A: The reading will give you an appreciation of the heat that your driveline oils have to endure while lubricating and protecting your driveline components. 

Q: So a lower temperature is better? 

A: Yes, as if an axle or gearbox is not operating efficiently more heat will be generated. Component design and usage has a significant impact on the temperatures. However under all conditions, choosing the right high performance gear and axle oils can help contribute to a more efficient driveline and longer component life.

The Shell Spirax range of axle and gear oils offers proven protection, including the latest synthetic oils that deliver exceptional wear, pitting, bearing-failure and corrosion protection for heavy-duty axles, transmissions and gears operating under highly stressed conditions. This can help to reduce your costs.

Q: I get a high temperature reading. Do I have a problem?

A: High temperature in itself does not mean there is an immediate problem. However, there are a lot of failures that will cause a high temperature in your driveline. There are a few things to consider. 

Generally, under higher temperature your driveline oils deteriorate faster through oxidation. Through high heat, the oil and the additives react with oxygen and thereby lose their intended properties. Sometimes, oxidised components can form tough layers of varnish or lacquer that stick to driveline components changing internal tolerances, or form sludge that blocks lubrication passages potentially starving parts of the driveline component from lubrication or damaging the internal controls of robot-controlled and semi-automatic gearboxes.

When heat is a consequence of prolonged high loading, the so-called extreme pressure (EP) additives intended to prevent metal-to-metal contact could be depleting faster than intended, increasing risk of component wear or even failure.

If you have a high heat reading, you can consider the following: 

Q: Did you follow your Original Equipment Manufacturer's (OEM) advice as to axle and transmission maintenance schedule and minimum specifications and maximum allowable oil drain intervals? 

A: If possible, consult your service manual or certified mechanic as to the maximum allowable temperatures in the driveline components.

Q: Did you perform an unusual heavy driving cycle, i.e. drive a heavy load up a long steep incline? 

  • A: If you had a particular peak load, it may be advisable to apply a second Heat Tester to measure again to verify if the high temperature is associated with that peak.
  • A: If not, your driveline may be overloaded and/or your driveline oils no longer protecting your equipment adequately. It may be advisable to seek qualified technical advice.

Q: I maintain a fleet of multiple vehicles and have a structured maintenance regime. How are these Heat Testers relevant for me?

A: If you are running a fleet of similar vehicles being operated under similar conditions, these Heat Testers can help in a variety of ways: 

  • Between similar vehicles under similar running operating conditions, a variation in temperature readings between vehicles might indicate a possible component issue.
  • The Heat Testers can be inspected with regular inspections for any high reading which can be recorded against any issues that may come to light later during maintenance (such as unexpected high wear or premature failure)
  • When comparing similar vehicles, the effect of using different oils on driveline temperature and thereby driveline efficiency can be observed.

Q: How can I ensure my driveline temperatures are as low as they can be?

A: If your driveline components are well maintained and in good working order, choosing the right high performance gear and axle oils can help contribute to a more efficient driveline and longer component life.

Comparing a Spirax 85W-140 mineral with  Spirax 75W-90 synthetic oil, a 10 degree difference in gearbox temperature has been observed under controlled conditions as is visually demonstrated in this video.

Please use Shell LubeMatch to select the axle and gear oil products suitable for your vehicle available in your market that will support you achieve the optimum driveline efficiency.

Follow your manufacturer’s lubrication specification recommendations. However, if you are operating your driveline components beyond your Original Equipment Manufacturer's (OEM) recommended limits, it is advisable to seek specialist advice with regard to driveline lubrication.

For more information about our complete offer for the on-highway transport sector, please see our Fleet sector pages

For feedback and questions regarding the Heat Tester, you can contact us here

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