Maintaining your Gearbox: Some Tips

Your gearbox is essential to the efficient operation of your car. It is an expensive component to replace, so it’s important to take good care of it. One gearbox maintenance task that can be tackled on a DIY basis is replacing old oil with new.

Car gearbox

What the gearbox does

Before we look at how to change your vehicle’s gearbox oil, it’s worth a brief comment about why this is necessary from time to time. Your gearbox allows the power generated by your engine to be applied to the wheels incrementally. In other words, it ensures that the energy is delivered in the most efficient manner based upon gearing that is most appropriate for the speed you’re travelling at. This inevitably involves a large number of metal parts moving at speed alongside and against each other, which in turn creates friction, leading to some of the engine’s energy being transformed into heat rather than a motive force for your vehicle. This is inefficient, expensive in terms of fuel consumption and ultimately damaging to your gearbox through unnecessary wear and tear. Using the right oil inside your gearbox is therefore essential to help reduce that friction.      

The problem and solution

Unfortunately, as your gearbox oil ages, it loses some of its friction-reduction capabilities. That is why most car manufacturers will recommend that it is changed after a specified number of miles/kilometres (typically somewhere around 30,000 miles/50,000 kilometres). Some people prefer to leave this to a garage but it is perfectly possibly to do it yourself if you have a few basic tools and can safely get underneath your car. The first important tip in how to change your vehicle’s gearbox oil is to carefully read your owner’s manual. Different vehicles use quite different approaches for changing gearbox oil and no general guide can describe them all in detail. Be clear that you understand what tools you will need and have purchased the correct oil recommended in your manual.


The method

Once you have the tools, raise your car above an inspection ramp or on professional axle supports. Under NO circumstances should you use improvised supports such as bricks or wooden planks – they are highly dangerous. Once your vehicle is safely elevated, slide underneath and locate the gearbox as per the instructions in your manual. Your gearbox may have one of several different methods for both checking the oil level and draining/filling it, and again your manual will clarify how to approach both tasks. This should generally be done when your engine is warm so that the oil will drain easily. Before draining, check your oil levels. If they are lower than they should be, it might indicate a leak – something that would be perhaps best left to a garage to investigate.

Otherwise, drain the oil. Note that draining usually involves removing a plug and a special manufacturer’s tool may be required in order to do this. In some cases, your gearbox might only have a level tester (dipstick) and filler cap. If so, you will need to remove the old oil with a pump or syringe. Drain the old oil into a suitable receptacle and dispose of it in accordance with your local environmental laws. Fill with the appropriate oil and wipe all surfaces clean. Replace all removed plugs and the job is done.     

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