Why Change Transmission Oil


The interest in emptying a gearbox

Transmission Oil Characteristics

Gearbox oil prices

How often should the oil be changed?

The gearbox is an essential element in the powertrain of a motor vehicle.

Its technology is as complex as that of the engine; hence, we’ll talk about the need for regular maintenance and oil changes in this post.

The interest of draining a gearbox

Although less stressed than in the engine, oil plays a vital role in the engine: it lubricates the gear trains, bearings and synchronizers.

Its main qualities are :

  • its resistance to pressure;
  • its resistance to shear;
  • its high lubricating power;
  • its cleaning action (it must rid the gearbox elements of the inevitable metallic particles due to wear).

It is, therefore, necessary to replace used oil regularly to ensure the durability of the gearbox.

Characteristics of gearbox oil

There are mainly two types of oil corresponding to two types of gearboxes.

Mechanical gearbox

SAE EP75W80 or EP80W90 oil are the most common; the most commonly used on light motor vehicles is SAE EP75W80 :

SAE (Society Automotive Engineers): This standard exclusively defines the oil’s viscosity (index 75 is less dense than 90).

EP (Extreme Pressure): this term defines the paramount quality of gear oil, which must resist rolling caused by the gear teeth’ rotation.

Automatic transmission

The automatic transmission oil is red and marketed by different oil tanker brands. It is specific and is not miscible with the previous oil in the transmission. Here, we are referring to the world’s famous Dexron ATF oil.

Gearbox oil prices

EP 75W80 oil costs about $6 to $8 per litre, while ATF oil costs $10 to $15 per litre.

These 2 types of oil can be easily found in all automotive supply industry (garages – equipment manufacturers – supermarkets – Internet sites…).

The quantity of oil required is 2 litres, up to 3.5 litres for a mechanical gearbox and 3 to 7 litres for an automatic gearbox (consult the manufacturer’s data).

For the operation carried out by a professional, it can result in a fixed price or a time scale generally equivalent to half an hour ($25 to $30), to be added to the oil price.

How often should the oil be changed?

It is determined by mileage and duration (for example, every 10,000 km or every 2 years).

It is very variable (consult the manufacturer’s recommendations) and can be done every 2 years as if it were never done.

Indeed, some manufacturers recommend lifetime lubrication. Normal vehicle maintenance operations (replacement of the transmission or bellows, clutch, leaks, etc.) often require the gearbox to be drained, and it can be estimated that in the life of a vehicle, this operation can be carried out once or twice (at worst, every 100,000 km).

In this situation, it is better to play it safe; an oil change every 2 years will preserve the reliability of the gearbox as it will provide:

  • the evacuation of metallic particles;
  • the elimination of traces of water in the oil (condensation).

As you have understood, it is better to do more than is necessary. If you want a long life for your vehicle, set the time for the transmission oil change systematically below the manufacturer’s recommendations. As the saying goes, prevention is better than cure!

Hope the above has helped you better understand a gearbox oil change, so next time your mechanic talks about the need for a transmission oil change for your car, you’ll know what he is talking about.

You might also be interested in What is Gearbox Oil

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