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Gearbox Oil: What You Need To Know

When it comes to car oil maintenance, it’s usually engine oil that gets all of the attention. While engine oil is obviously of great importance, gearbox oil is generally forgotten about, and not enough motorists give sufficient consideration to this vital fluid. As it is rarely visible and is not liable to cause problems over the course of the average car’s life, it’s easy to think that gearbox oil just gets on with its job without the need for regular inspection or maintenance. However, as with most components in your car, if it goes wrong, it can be highly dangerous.

Take a look at our handy guide to gearbox oil below, complete with advice about how to recognise and solve any problems it may cause…


What Is Gearbox Oil?

Without stating the obvious, gearbox oil is a lubricant found in the transmission system to reduce wear and tear on the internal mechanism. It has a strong sulphur-like smell and is usually a hypoid oil that contains extreme pressure additives for higher performance ability.

It has a higher viscosity than engine oil, better protecting the gears and ensuring a smooth transition between them. The viscosity is also essential as there is no pump to push oil around the gearbox, and only the lowest gears are submerged in lubricant.


How Do You Know If Gearbox Oil Needs Changing?

There is a lot of debate over how often gearbox oil should be changed. Some experts suggest every 50,000 miles, some say hundreds of thousands, while many car manufacturers claim that the vast majority of new designs will never require a gearbox oil change (although this may just be marketing rhetoric).

If healthy, gearbox oil should be slightly red in colour, and should not emit a strange burning smell. A grinding noise from the clutch or slipping gears are common indicators of faulty gearbox oil, and checks should be carried out immediately. Defective fluid can be highly damaging to your car’s transmission and gear operation, resulting in a slow gear shifting response or corrosion of internal mechanics.

To test if your oil needs changing, your vehicle will first need to be raised using either a lift or appropriate jacks. Ensuring that the car is level, carefully unscrew the fill cap on the transmission system to access the gearbox oil, checking the level with a ruler or screwdriver and examining for any irregularities.

(If your car uses an automatic transmission, you should be able to check the oil level and quality using a dipstick, similar to how engine oil is checked).


How Is Gearbox Oil Changed?

Changing gearbox oil is a relatively simple process, although it’s highly recommended that it be carried out by a professional. It should cost around £50, so be wary of any garage that charges drastically more than this estimate.

Should you wish to perform the oil change yourself, however, start by getting yourself a bucket, or else things could get messy very quickly! Next, locate the drain plug and loosen it until oil begins to spill out, leaving it to drain for around half an hour or until every last drop has emptied into the bucket. Secure the drain plug firmly back into place, and remove the filler plug. Suspend the replacement oil container above the gearbox, and attach a plastic tube between the bottle and the filler hole, after briefly syphoning the oil to initiate the flow. Leave to fill for another half an hour or so, regularly checking the oil level, before removing the tube and screwing the filler plug back into place.



The expert mechanics at Oaks Services have the skill and experience to perform gearbox oil checks and replacements on all vehicle types. If your transmission requires more than an oil change, however, we can also carry out full gearbox repairs and replacements in a quick and efficient manner to ensure that your car is back on the road as quickly as possible.
For more information, or to book your full service, contact our friendly team today.