6 Symptoms That Indicate Problems in the Automatic Gearbox of Your Car

Automatic gearboxes are not as ubiquitous in our country as in other European countries or in the United States, but during the past decade they have become enormously popular. Currently, many cars do not even offer traditional manual transmissions as an option. Unfortunately, it is a more complex mechanical element, with specific maintenance and the possibility of costly breakdowns - which in many cases require dismantling or rebuilding the gearbox. These are the six most common symptoms of problems with your automatic gearbox.

There are many types of automatic transmissions

Before we get into flour, there are many types of automatic gearboxes. The most ubiquitous and to which much of this article refers are torque converter changes . This system is driven by oil pressure and is the smoothest, in addition to being the "lifelong" automatic gearbox - it has been with us for more than half a century. On the other hand, and with different problems, there are the double-clutch automatic transmissions , which have been with us for more than 15 years. Finally, there are robotized manual gearboxes , which are for almost all purposes, a manual gearbox without a clutch pedal.

The guide is focused on automatic torque converter shifts.

Nor can we forget the continuous variator changes , very common in hybrids, but also present in conventional cars - especially in Japanese models. The only common feature between all of them is that they are driven with two pedals, but they have inherently different operations. Therefore, we will focus this article on torque converter changes . Soon we will dedicate more space to breakdowns in other types of automatic transmissions.

1) Vibration when accelerating or idling

In this case, the vibrations would be especially noticeable when accelerating with a low or medium throttle load. It is convenient to look at the rev counter, and see if the needle oscillates. These "hesitations" can also be caused by elements of the engine such as a dirty EGR or bad injectors , so it is important to isolate the symptoms from the rest of the possible faults. In the case of the change, this would indicate a problem in the drum where the clutch discs are housed or in the transmission input shaft itself. These vibrations or jerks can be associated with difficulty changing gear.

It's not good news.

2) Does not change gear, or takes a long time to do so

It is one of the most elusive symptoms of an automatic gearbox failure. The failure may be caused by the electronics, or it may be caused by a degraded ATF fluid, at the wrong level , or that has lost its properties due to age and lack of maintenance. The consequence is inadequate pressure in the torque converter, by default or by excess. The lack or excess of hydraulic pressure will prevent the clutch discs from performing their function correctly and the gearbox will behave erratically.

It is vital to keep an eye on the ATF fluid level, and change it when necessary.

3) Knocks when changing gear

This problem usually occurs when hot, and also when moving from D to neutral or reverse. The knock is usually caused by a problem in the valve body of the automatic gearbox . The failure of these solenoid valves can be reflected in a failure warning light if the car is modern enough. The valves are integrated into the mechatronics of the gearbox - they are controlled by electronics, but they are mechanical components - and fixing the fault would usually require the help of a professional.

4) Does not move, neither forward nor backward

If the car does not respond to our inputs and is unable to move in any direction, the most plausible thing is that we have a fault in the oil pump of the gearbox itself . With no oil pressure, the torque converter will not be able to transmit the power of the engine to the gearbox clutches, and we will literally be unable to move. It can also be caused by a catastrophic gearbox failure , but the symptoms prior to that failure would have been noticeable for thousands of miles - it would not be a sudden, sudden failure.

Another possible cause may be a faulty lever linkage.

5) The change "slips" when changing gear

It is one of the most common breakdown symptoms in an automatic gearbox. If you notice excessive slippage when changing gear, the problem clearly indicates wear on the automatic gearbox clutches . It is a dangerous breakdown - just as it is in a manual car - since we can be left without a response from the car when we need it most. It is a fault that will go further and will end up making driving practically impossible. In some cases it could show a problem derived from a low level of ATF, but generally it will be time to open the box and change your clutches.

A similar breakdown is to be expected if the car takes a long time to engage D or R.

6) Smells burnt

Houston, we have a problem. A burning smell in the car is never good news. If the smell comes from the transmission, it is most likely that we have an overheated transmission oil . ATF fluid degrades at high temperatures and loses lubricating properties. You can imagine the result: accelerated wear due to excess friction , metal remains inside the gearbox, and all the problems that this entails. Run to the workshop to solve the problem, and drive your car as little as possible if you detect the problem.

A high temperature could be a problem with the transmission cooling system, or with an insufficient level of ATF.

What is the solution to the failure of the automatic gearbox?

In some cases, an automatic transmission fluid replacement may fix the problem , and should be the first thing done before heading into more swampy waters. If the problem persists, there will be no choice but to disassemble the transmission from the car to send it to an automatic transmission specialist. We may be facing a wear problem in the pinion gear, or we may be talking about generalized wear that motivates the need to rebuild the gearbox. A rebuild should not be necessary before 250,000 km of conventional car use, and on many cars it may never be necessary.

Breaking down an automatic gearbox is usually expensive, and often requires a transmission specialist.

However, it is an expensive operation with a bill that will go into the four figures. That is why it is very important to change the transmission fluid (and its corresponding filter) when the car manual specifies it - or to advance its maintenance - and follow the manufacturer's recommendations for use. It's also not a bad idea to treat the car gently : we should especially avoid aggressive driving in the cold - something that will come in handy for the engine, by the way - since the lubrication of the internal components of the gearbox is not optimal at that time.