Signs of transmission problems: When problems arise with an automatic transmission, it almost never happens suddenly. Some symptoms creep in gradually and can even go unnoticed, ignoring these symptoms can develop into a full-blown defect. In this article, you will find out how to recognize typical problems with an automatic transmission and what you can do about it. We also list the most common problems and symptoms that you have to be on the lookout for.
An automatic transmission is a spectacular thing that brings you comfort and enjoyment. All you do is shift into drive “D” and no matter what speed you are travelling at, the right gear is automatically selected. However, this comfort can also have its downsides. Since you don’t have to concentrate on anything further behind the steering wheel and the brake pedal, signs of transmission problems can go unnoticed. In a vehicle with a manual gearbox, problems can draw attention to themselves a little more clearly – for example, when individual gears are difficult or hard to engage, the clutch slips or the manual gearbox as a whole is jittery.
How do transmission problems become noticeable?
With an automatic transmission, signs of transmission problems can show up in many different ways. Here are the typical examples:
- Jerky, rough gear changes
- Delayed transmission engagement
- Gear changes are delayed when the engine is cold
- Severe hum or vibration
- Some gears are no longer engaging
- Metallic grinding or grinding noises
- A “burning” smell
- No more drive, neither forwards nor backwards
It is becoming increasingly difficult even for professionals and for some auto repair shops to find the real causes of problems with automatic transmissions. One of the reasons for this is the large number of gearbox variants that are now on the market. They are technically very advanced, significantly more complex than older types of automatic transmissions, and many are controlled by what is known as a TCU, an electronic transmission control unit (read more about the TCU on Wikipedia). All of these factors make it difficult for non-specialist workshops to reliably diagnose and repair.
Signs of transmission problems and the most common causes
Automatic transmission jerks
If the automatic transmission slips or it jerks when changing gears and even jerks when stationary, the cause may be damage to the torque converter or the clutch plates. It is not uncommon, however, to have a slide switch problem.
Automatic transmission only drives backwards
When trying to shift into drive, does the car not move and you can only go in reverse? Then the problem usually comes down to mechanical damage to the forward clutch. But it could also just be that the clutch plates are worn.
The automatic transmission does not shift
If the automatic transmission can no longer be shifted or is difficult to shift, or if it blocks and no longer takes any gears, the selector lever module, the PRND switch or the brake light switch could be defective. However, there may also be internal mechanical gear damage.
The automatic transmission shifts hard when it’s warm
Shifting hard when it is warm is a sign that there is a problem with the pressure level inside the transmission. Read more about why your transmission is experiencing hard shifting.
The automatic transmission shifts improperly
In the case of improper shifting or the shifting of the automatic transmission, the probability is high that the transmission oil is already old. A transmission oil flush or an automatic transmission oil change is advisable. However, the cause can also be due to the slide switch, a defect in the solenoid valve, the control unit or incorrect adaptation values or the old software version.
The automatic transmission has no drive
If there is no longer any frictional connection, the car no longer drives and suddenly the drive is missing, there may no longer be a connection between the converter and the input shaft of the transmission. This means it could have been torn off. It is not uncommon for the turbine wheel inside the torque converter to be defective or for the oil pump to be damaged.
The automatic transmission does not pull properly
If the automatic transmission does not take on the gas or does not pull the car properly, the cause could be torque converter damage. Wear of the clutch plates in the transmission would also be possible.
Automatic transmission makes noises
For example, if the automatic transmission whistles when accelerating or makes other unusual noises while idling or while driving, the problem may be a torque converter failure, differential failure, bearing failure, or damage to the planetary gear sets in the transmission.
Automatic transmission shifts to N while driving
If the transmission simply shifts to N while driving, there may be a shift slide problem or a defect with the transmission control unit.
Automatic transmission smells unusual
If the automatic transmission smells of burnt oil or rubber, then it may be that the transmission is losing oil or that the transmission oil level is too high. This causes the oil seal to leak. Sometimes, the cause is a torque converter or oil pump damage.
The automatic transmission has too much slip
If too much slip is noticeable in the automatic transmission, this indicates the wear of the clutch plates or the converter clutch.
The automatic transmission shifts up too early
If the gear changes are too early, the software version on the gearbox control unit should be checked. The adaptation data may be incorrect or the gearbox control unit is defective. Otherwise, a sensor error in other assemblies can also be responsible, for example, ABS system electronics.
Automatic transmission shifts too late
If the transmission shifts down the gears too late or too late, this is probably due to a pressure problem.
Automatic transmission goes into the emergency program
If the automatic transmission suddenly switches to limp-home mode, it may be due to an internal mechanical transmission problem, a problem with the transmission electronics or a defect within the speed sensor.
The Most Common Reason For transmission problems: Bad transmission oil/fluid
As we mentioned some symptoms can show up as a result of various mechanical or electronic issues. However, it is not uncommon for the cause of problems to be found in the fluid or oil of the automatic transmission, especially with shift bumps or shift delays. In addition to a low fluid level, the age and state of the oil, in particular, can cause problems with the automatic transmission.
Many manufacturers promise a “lifetime” transmission oil life expectancy, which is simply not true and should be avoided at all costs. Transmission oil or fluid needs regular changing, just like your engine oil. The oil change interval is usually longer, but should never be ignored. Especially if you often drive short distances. The truth is, transmission oil also ages over time. Depending on the mileage, driving style or external influences, it loses its viscosity and lubricity and impurities, foam or oil sludge can form in the automatic transmission.
If you do not replace your automatic transmission fluid regularly, proper lubrication cannot be achieved and wear increases significantly – so much, in fact, it can lead to a full-blown defect of the automatic transmission. The change interval depends on many individual factors, but if you want to be on the safe side, check the oil level from 50,000 kilometres or have the oil change carried out every 60,000 to 80,000 kilometres.
Another way to prevent gearbox damage is to flush the gearbox, which is carried out with a special flushing device. While for technical reasons only about half of the oil can be changed when changing the transmission oil, thanks to the transmission flushing it is possible to completely renew the entire automatic transmission fluid and also to completely flush the transmission oil lines.
Learn how to check other car fluids by reading our guide!
When it comes to cars people want two things: quick and cheap. Trust us, that doesn’t go well when it comes to automatic transmissions. The most important part of automatic transmission repair is the correct diagnosis. A good mechanic will recognize the common signs of transmission problems and diagnose based on his judgement and experience. Sometimes the problem is not even on the automatic transmission. In order to shift gears smoothly, the TCU gathers information from engine electronics which can also fail and cause jerky shifting. That is also the reason why you should never trust your automatic transmission to a non-professional who fixes things for “cheap”. This route might just leave you spending a lot more than you would by trusting a professional in the first place.
As already mentioned, an automatic transmission oil change can be sufficient to resolve a number of issues. If you just bought a used car, make sure the transmission fluid has been changed. Replacing a torque converter, on the other hand, is often the solution if the vehicle cannot be driven forwards or backwards. Whatever the fault, the clear advantage of a repair is the cost factor, don’t let the dealerships tell you that you just need a new transmission. Always replace the parts that are actually affected by a defect. Specialized workshops that do nothing other than repair and overhaul automatic transmissions every day, know the typical problems and signs of transmission problems. They have the right spare parts in stock and can therefore eliminate the problems quickly and inexpensively.