How does gearbox oil work?
How does gearbox oil work?
Gearbox oil (also known as transmission fluid) is a special type of lubricant that helps your car’s gearbox run smoothly. It reduces friction between moving parts, prevents excessive wear, and keeps everything operating quietly and efficiently.
In manual gearboxes, main job is to lubricate the gears and internal components. But in automatic gearboxes, it also powers the hydraulic system that controls gear shifts — making it a critical part of how your car changes gears.
Gearbox oil also helps cool the transmission, preventing it from overheating, especially during long drives or stop-and-go traffic.
Over time, the oil can break down or become contaminated, which affects how well your gearbox performs. That’s why regular gearbox oil changes are important — they help keep gear shifts smooth, protect internal parts, and reduce the risk of costly repairs.
How to check gearbox oil level?
Checking your gearbox oil level depends on whether your car has a manual or automatic transmission — and not all vehicles make it easy.
For manual gearboxes:
Most modern manual cars don’t have a dipstick for gearbox oil. Instead, the oil level is checked by removing a filler plug on the side of the gearbox — something best done by a mechanic, as it usually requires the car to be lifted and safely supported.
For automatic gearboxes:
Some automatics do have a transmission fluid dipstick, similar to the engine oil one. If your car does, here’s how to check it:
1. Park on a level surface and keep the engine running (unless your manual says otherwise).
2. Engage the handbrake and cycle through all the gears (P → R → N → D) then leave it in Park.
3. Locate the dipstick — usually marked and found near the back of the engine bay.
4. Pull it out, wipe it clean, reinsert it fully, then pull it out again to check the level.
5. The fluid should be between the “MIN” and “MAX” marks, and a reddish or pinkish colour. If it’s low, dark, or smells burnt, it may need topping up or replacing.
What does a gearbox oil change job involve?
Here’s what happens during the process:
The mechanic will check the gearbox oil level and condition. If necessary, they will safely lift the vehicle and prepare the gearbox for the service.
The old gearbox oil is carefully drained to remove built-up contaminants that may affect performance.
The mechanic will refill the gearbox with fresh, manufacturer-recommended oil to ensure optimal lubrication and smooth gear transitions.
They will engage the gears to help the new oil circulate properly through the system.
The vehicle will be tested to confirm that the gearbox is functioning smoothly with the new oil.
How do I know if I need a gearbox oil change?
Here are some common signs that your gearbox oil may need changing:
If the gearbox oil appears dark, cloudy, or has debris in it, it may no longer be providing proper lubrication.
Struggling to shift gears or experiencing a rough transition between them can be a sign of old or low gearbox oil.
Some vehicles have a gearbox temperature or transmission warning light that may illuminate when the oil is low or has deteriorated.
If you hear grinding, whining, or knocking sounds from the gearbox, the oil may not be protecting the internal components effectively.
If you notice any of these symptoms, having your gearbox oil checked and replaced, if necessary, can help maintain smooth performance and prevent costly repairs.
How often should I change my gearbox oil?
Most manufacturers recommend changing the gearbox oil every 30,000 to 60,000 miles (or every 4–5 years). If you regularly drive in stop-start traffic, hilly areas, or tow heavy loads, it’s worth checking it closer to 30,000 miles.
For most automatics, the fluid should be changed every 40,000 to 60,000 miles. Some newer cars have “sealed for life” transmissions, but even these benefit from a fluid change around 60,000 miles to keep things running smoothly.
Always follow your car’s service schedule or ask a trusted mechanic for advice. Fresh gearbox oil helps extend your transmission’s life and ensures smoother gear changes.
How do I know if I have a gearbox oil leak?
A gearbox oil leak can cause serious issues with your vehicle’s performance if left untreated. There are a few common signs to look out for, one of the most noticeable being finding reddish-brown or dark oil spots under your car, typically beneath the middle where the transmission sits. This oil often has a strong, unpleasant smell.
You may also notice that the car becomes harder to drive smoothly. If it’s more difficult to change gears or the gearbox feels like it’s slipping or grinding, low oil from a leak could be the cause. Some leaks can also cause unusual noises, like whining or clunking, when the car is in motion, especially if the gearbox isn’t getting enough lubrication.
Another warning sign is a burning smell, which can happen if oil leaks onto hot engine parts. In some cases, a warning light might appear on your dashboard, like the check engine light, if the leak is affecting how the transmission works.
If you suspect a gearbox oil leak, it’s best to have a mechanic check it as soon as possible. Fixing the issue early can prevent more expensive repairs later on.
Does changing gearbox oil make a difference?
Yes, changing gearbox oil can improve gear changes, reduce noise, and help protect internal parts from wear. It also helps prevent overheating in automatic gearboxes and can extend the life of your transmission. If your shifts feel rough or the gearbox is noisy, a fluid change may help restore smooth performance.
How much does a gearbox oil change cost?
The cost of a gearbox oil change typically ranges from £70 to £120, with the average price around £85. However, the exact cost depends on your vehicle’s make and model, as well as the type of gearbox oil recommended by the manufacturer.
What does a ClickMechanic gearbox oil change quote cover?
Unless otherwise stated, the quote will cover:
* The cost of the gearbox oil
* The mechanic's labour for replacing the oil
* VAT (if applicable)
* 12-month parts and labour warranty
Can the gearbox oil be changed by a mobile mechanic?
Yes, a gearbox oil change can be carried out by a mobile mechanic, making it a hassle-free alternative to driving to a garage. Since this service doesn’t require heavy lifting equipment or a workshop setup, a skilled mobile mechanic can efficiently drain and replace the gearbox oil at your home or workplace. Choosing a mobile service saves you time and effort while ensuring your vehicle continues to run smoothly with fresh, high-quality oil.
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Frequently asked questions about gearbox oil change & replacements
Read our answers to questions about gearbox oil change costs, symptoms and more.
What does Gearbox Fluid do?
The gearbox fluid is a fluid that lubricates the internal components of the gearbox, vital for keeping the internals running smoothly. If your car has an automatic gearbox, the fluid has an extra function in that it is also the fluid powering the hydraulic system, vital for moving the internal parts of the gearbox. Additionally, a steady supply of fluid cools the automatic gearbox.
What does a gearbox oil change involve?
- The mechanic will inspect the fluid.
- If necessary, the mechanic will replace the fluid.
- The mechanic will test drive the car and inspect the gearbox.
Can I do a gearbox oil change myself?
Unless you are a qualified mechanic with the required skills, training and equipment to do the job, we strongly recommend a gearbox oil change is only carried out by a professional mechanic. ClickMechanic can help get you a vetted and local mechanic to carry out the work. Just enter your postcode and your car's registration number at the top of this page and select the work needed to get an instant fixed price up front.
What are the symptoms of bad gearbox fluid?
- When the gearbox's fluid has discoloured.
- When you have trouble changing gear.
- When the gearbox temperature light on the car's dashboard is on.
- When there is a grinding noise coming from the gearbox.
How long does it take to change gearbox oil?
A gearbox oil change usually takes around 1 hour, but can take less or more time. Ultimately, the time that the job will take will depend on a number of factors, like your vehicle's make and model, year, as well as other factors. Select your car at the top of this page for information on job time and cost for your vehicle through ClickMechanic.
How often should you change your gearbox oil?
Most manufacturers recommend that you change gearbox oil at between 30,000 and 60,000 miles and at regular intervals after that. If you do a lot of driving in urban areas, where you’re often changing up and down through your gears, you drive your car for a living so the gearbox gets plenty of use, it’s sometimes advisable to change your gearbox oil as often as every 15,000 miles.
Always service the gearbox fluid as and when stipulated in the guidelines set out by your car's manufacturer. It is essential that the fluid is kept in superb condition to ensure the gearbox does not suffer from excessive wear or damage. This should contribute to a prolonged and unproblematic gearbox lifespan.
Should you experience problems prior to the next scheduled service as stipulated by the manufacturer it is important to have the gearbox inspected and, if necessary, have the gearbox fluid replaced.
How to extend the life of your gearbox oil?
Like any kind of greasy substance that you put inside the workings of your car, gearbox oil will lose its effectiveness over time. It can also leak, and if you spot such a problem, you should always get it investigated, and the oil topped up if necessary.
If you change gears gently, you will be giving yourself a good chance of extending the time between two gearbox fluid changes.
Using a more heat resistant synthetic oil can also contribute to a longer timespan.
Does changing gearbox oil make a difference?
Yes, the gearbox oil protects a variety of moving parts, and these can be damaged if the oil isn’t up to the job. The fluid in your gearbox can become contaminated with other liquids and if you even occasionally change gears roughly, this can deposit tiny pieces of metal shavings into your gearbox oil. These stop it from working as effectively as it should, and shorten the life of your whole gearbox and in the worst case, cause serious damage.
Does gearbox oil need to be changed?
Yes, it is important to replace the gearbox oil as per the guidelines set out by your car's manufacturer. As the gearbox oil protects a gearbox's moving parts it's worth making sure the gearbox oil is in good condition to prevent damage and improve performance.
Can I still drive with bad gearbox oil?
Manual gearboxes are closed units and their operation is dependent on the quality of the oil contained within them, much like an engine requires good oil. Unfortunately, before issues become apparent to the driver, the damage is already done. If you suspect there is any issue with the gearbox oil or there are concerns about its age or condition, book an inspection with a professional mechanic with immediate effect. Driving the vehicle with bad gearbox oil may lead to further complications or damage to your gearbox.
Is dirty gearbox oil an MOT failure?
No, dirty gearbox oil will not lead to an MOT failure. The inner workings and hence fluid are not assessed during an MOT as only safety-critical and structural issues are checked for (for example transmission joints or bearings are checked).
How much is a gearbox service?
A gearbox service for an automatic car can cost from £150 to over £250, depending on the type of gearbox and the parts required.
What is a gearbox service?
A gearbox or transmission service on an automatic car differs from a simple gearbox oil drain & refill in that it involves the replacement of a filter as well as a gasket or sealant. During a gearbox service the mechanic would lift the car and drain any fluid before the sump is removed to clean transmission parts and replace the filter. Once the sump is refitted with the new gasket or sealant the transmission unit is filled with new ATF again. Manufacturer procedures are followed during this process, which may involve plugging in a diagnostic tool to run the transmission through the process. Eventually the gearbox is run through the selection routine to ensure it runs smoothly.
When should a gearbox be serviced?
A gearbox should be serviced according to the recommended manufacturer service schedule or if an issue with the gearbox has been identified. For example, if the gearbox fails to change gears, there is a jerky gear shift or the transmission overheats a gearbox service may help remedy these issues.
How do I know if my gearbox oil is low?
There's a number of tell-tale signs that can indicate that the gearbox oil level is low:
- Trouble shifting gears
- Gearbox overheats
- Noises from the gearbox
- Delayed engagement of gears
- Vibrations from the gearbox
Where can I check gearbox oil level?
You can usually check the gearbox oil level via a gearbox oil dipstick in the engine bay of your car. Some cars may not have one, then check the owner's manual for instructions on where and how to check the oil level. Often it will mean that you will need to lift the vehicle and check directly on the transmission by removing the oil fill cap and inserting a manufacturer advised tool to check the level and condition.
What is gearbox fluid flush?
An automatic transmission fluid flush or gearbox fluid flush is a process in which all of the old, dirty fluid is flushed out of the transmission and replaced with new, clean fluid. This helps to keep the transmission running smoothly and helps to prevent more complex and expensive problems with the transmission
Can I add gearbox oil without flushing the old oil?
Technically you can do it but is not recommended as not carrying out a flush means the transmission system will still have old fluid, debris, particles and deposits that can cause a transmission failure.
What happens if you put too much transmission fluid or gearbox oil in your car?
Overfilling with transmission fluid can lead to the leakage of the fluid from the gearbox. In some cases, it can cause the transmission to overheat and fail.
What is the difference between transmission fluid and gearbox oil?
Transmission fluid is a type of hydraulic fluid that is used to power automatic transmissions (in an automatic car). Gearbox oil is a type of lubricant that is used to protect and lubricate the moving parts in a gearbox (in a manual car).
What happens if I don’t change the automatic transmission fluid at it's recommended time?
If you don't change the gearbox oil when recommended, it can become contaminated. It may slip or may not shift gears properly and can also cause damage to the clutch system.
How much does a gearbox oil replacement cost?
A gearbox oil change generally costs between £70 and £120 with an average price of £85. Ultimately, the cost of a gearbox fluid replacement depends on your car and what parts your car's manufacturer recommends using for the replacement. Find out what you could save by having your gearbox fluid replaced by ClickMechanic by selecting your car at the top of this page!
Check out the ClickMechanic price for a gearbox oil change. See the averages for different makes below. We consolidate industry standard data with millions of data points to give you the most accurate price. These estimates may include Manual transmission oil.
| Name | Average Cost | |
|---|---|---|
| Audi | £122 | Get exact price |
| BMW | £99 | Get exact price |
| Citroen | £94 | Get exact price |
| Ford | £120 | Get exact price |
| Land Rover | £93 | Get exact price |
| Mercedes-Benz | £125 | Get exact price |
| Nissan | £103 | Get exact price |
| Peugeot | £114 | Get exact price |
| Renault | £120 | Get exact price |
| Toyota | £109 | Get exact price |
| Vauxhall | £108 | Get exact price |
| Volkswagen | £122 | Get exact price |
Estimates on average repair costs, such as the above results for a gearbox oil change, are based on ClickMechanic's quote data which combines multiple third-party sources. Actual costs may vary. We provide estimates on average repair costs for information only and accept no liability for any inaccuracies or errors. If you think an estimate is incorrect, please contact us to let us know.
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Mechanics that undertake gearbox oil work
- Ardamotive, Southampton
- Attleborough Service Centre (norfolk) Ltd, East Harling
- B J Mccaffrey, Bristol
- Complete Motor Care Ltd, Whitstable
- Croydon Vehicle Services LTD, Croydon
- DPT COMMERCIAL LTD, Kings Lynn
- Direct Automotive And Performance Tuning Ltd, Featherstone, Pontefract,
- FR Diagnostics, Leicestershire
- Hampshire Tech Automotive, Andover
- Old Mill Motors (witney) Ltd, Witney
- RD9 Automotive Group, Tunbridge Wells
- Rossway Services, Berkhamsted, Hertfordshire