Common Car Gearbox Problems And Why They Occur

Any car enthusiast can attest to the joy of switching gears as they cruise along the highway in their cars, irrespective of it being manual or automatic. The gearbox is the key component that ensures smooth transmission of power from the engine to the wheels, consequently altering the car’s speed. These same enthusiasts can also attest to the hassle of dealing with a faulty gearbox. Even the highest quality gearboxes can experience wear and tear over time, leading to performance issues or in extreme cases, a stranded vehicle. Therefore, as a car owner, you need to understand some of these potential problems. But before that, here is a small crash course on how a gearbox works.

Understanding the Car Gearbox

A typical gearbox has a few core components: clutch shaft, countershaft, main shaft, gears, and bearings. The clutch shaft, as the name suggests, is connected to the clutch, which in turn is connected to the main engine crankshaft. Its torque matches the power generated by the engine. Next is the countershaft, which is connected to the clutch shaft via gears. According to the gear ratio, its speed can match the engine or be higher or lower. Lastly, the main shaft is connected to the transmission of the car. Hence, the speed of the main shaft matches the speed of the vehicle.

Thus, a gearbox alters gear ratios by switching between different gears, which alters the speed of the main shaft, and in turn, the speed of the vehicle. The first gear has the maximum torque production and minimal speed, and vice versa. Of course, in an automatic gearbox, this switching process is auto-regulated, whereas, in the case of a manual one, the driver has to engage the clutch pedal and change the gears to achieve the desired speed and torque.

With the basics out of the way, let’s take a look at some major problems plaguing the gearbox.

Common Car Gearbox Problems

1. Grinding or Shifting Difficulties

A common problem you can face with a gearbox is a grinding sensation or vibration, especially when shifting gears. It can be caused by gears with excessive wear and tear or damage. Lack of proper lubrication, such as low oil levels in the gearbox, can also be a culprit. In manual gearboxes, the grinding vibration or sensation can also occur due to a poorly engaged clutch.

While the probable causes are important to understand, it is pointless without understanding the symptoms, as it might be hard to pinpoint the jarring sensation in a moving vehicle. Some common indicators include a burning smell and a grating feeling while switching gears; that is, the switch is not smooth. You might also find metal debris or shavings in the gearbox oil.

So if you find any of these signs in your car, get them checked right away to avoid any major repairs down the road.

2. Gear Slippage

When you are driving, if you ever find that your car is not accelerating as fast as you expected, even when you are going full throttle, chances are gear slippage is the likely cause. This problem can create a loss of speed or acceleration in the car, thereby bringing down its performance. Gear slipping is also the likely cause if you notice some erratic shift when switching gears. The likely cause of this phenomenon is a worn-out or damaged clutch, low levels of lubricant within the gearbox, or damage in the gear-selecting mechanism.

So when you notice these symptoms, head over to your trusted garage or mechanic right away. They may change the clutch or oil levels within the gearbox. To prevent this problem, ensure that you are regularly inspecting your clutch and gearbox. With some routine maintenance and a basic understanding of the symptoms, you can prevent a complete gearbox overhaul.

3. Gearbox Fluid Leaks

Closely connected to the gearbox problems stated above, gearbox fluid or oil is very important to keep the friction between different gears to a minimum. Otherwise, it can accelerate the wear and tear on the gears, causing premature damage. Therefore, it is very important to watch out for leaking gearbox oil. If you encounter strange noises when switching gears, either manually or otherwise, find it difficult to shift gears, or perhaps notice some oil stains under your car, chances are your gearbox oil is leaking out.

But what can cause this leak? There are numerous probable causes, including damaged or worn-out seals, a crack in the casing, or malfunctioning gaskets. Hence, make sure you get it inspected at the earliest if you notice oil spills or strange noises in the gearbox. Otherwise, you may have to get the entire gearbox replaced, which can cost a fortune, especially if it is a relatively new vehicle.

4. Noisy Gearbox

Closely related to point A, the grinding or jarring sensation in a gearbox can also be accompanied by audible noise. The sound can be characterized as a clunking or thumping sound when the car is running, a crunching sound when you change gears in a manual vehicle, or feel a grinding sensation when it switches gears in an automatic transmission. Of course, this is very concerning news, and you need to get it inspected by a competent mechanic right away. But you must also know the probable causes of this clunking noise so that you don’t end up paying too much for repairs.

The main culprit behind a noisy gearbox is worn-out gears or even worn-out bearings. Although small, bearings are responsible for reducing friction between the gears, and a malfunctioning bearing can cause significant damage to a gearbox. Fortunately, with early intervention, you can prevent a major repair by simply getting the bearings replaced and ensuring proper lubrication.

5. Overheating

Overheating is always a cause of concern for cars. Often, the first notion is an overheated engine, but a gearbox is just as susceptible to getting overheated if the interior components are not working properly. How can you tell if your gearbox is overheating? The biggest telltale sign is a burning smell. If it is strong, stop your vehicle immediately and get it checked. You might also notice some slipping when shifting gears and loss of some power.

In a manual transmission car,  it is easy to pinpoint the cause of overheating, which is often a slipping clutch. The clutch is responsible for keeping the engine and gearbox disengaged when shifting gears. However, if the clutch malfunctions, that is, it slips, it can overheat the gearbox oil. This creates a strong burning smell. In such cases, replacing the clutch should be enough to resolve the problem.

If the problem lies in the gearbox itself, however, then the oil needs to be changed.

Why These Problems Occur

While the common causes of some of these gearbox-related problems have already been mentioned, in this segment, we’ll take a deep dive into the whys.

1. Manufacturing or Design Defects

Sometimes, the problem is not due to wear and tear or maintenance and can be attributed to a poorly designed gearbox. Although gearboxes and other parts are designed by CNC machining, it still doesn’t guarantee accuracy in every case. If the CNC machining services are not up to the mark, there can be a fundamental design flaw in the gearbox, leading to frequent and expensive repairs.

In such cases, it is best to contact the car manufacturer itself. The automobile company might go for a complete recall of the cars if it is a widespread problem. Alternatively, if the issue is not related to your gearbox, you can make a warranty claim and get it replaced for free or at a very small price. Either way, it is worthwhile to consider this probability if you are facing frequent problems in a newly bought vehicle or a newly installed gearbox.

2. Lack of Maintenance

Design flaws notwithstanding, the next likely culprit is a lack of proper, scheduled maintenance of the gearbox. A car requires regular upkeep to keep it running smoothly and ensure optimal performance. This means regular inspection and maintenance of various parts of the vehicle, such as tires, engine, transmission, and gearbox. Since it is concealed within the car, many motorists might not give it much thought until it is too late and the entire gearbox needs to be removed.

To prevent this, ensure that the gearbox is also regularly inspected during your scheduled maintenance. Check for oil spills, unusual vibrations, grinding or clunking noises, or burning smells from time to time. Although it is unlikely for gears and bearings to get worn down too quickly, it is important to keep an eye out for any of the symptoms mentioned above. Lastly, during your scheduled maintenance, listen to your mechanic and get the oil and small parts changed to prevent major hassles down the road.

3. Wear and Tear

Despite regular maintenance and a properly designed gearbox, with enough use and time, it will likely face some wear and tear. With numerous moving parts in the form of gears, bearings, and shafts, it is normal that they get worn down. Of course, it depends on how well you maintain your vehicle and how frequently you drive it. That being said, some minor or major gearbox repairs are inevitable after a few years. It could be as minor as an oil change, switching up a few bearings or gears, or as major as removing the entire gearbox and installing a new one.

Also, remember that certain driving habits are more likely to cause premature wear and tear in the gearbox, such as revving the engine when you are idling or going straight from drive to reverse without stopping in an automatic transmission. Moreover, if you are living in cold conditions, you should ideally allow the car to warm up a bit before you start driving, especially if it is an older model.

Last Words

To wrap things up, a gearbox is a wonderful piece of equipment that can be susceptible to major or minor damages. It is important to watch out for these signs to get them repaired or replaced a the earliest. Also, learning more about why it happens can help you prevent these repairs from occurring in the first place. So if you are not very car-savvy, we hope that this article helped you to better understand your gearbox and transmission.

Author’s Bio

Dhruv Mehta is a Digital Marketing Professional who works as a brand consultant and provides solutions in the digital era. In his free time, he loves to write about automobiles, business, finance & tech. Follow him on Twitter or connect with him via LinkedIn.