Technological advances mean that automatic transmissions are becoming more and more widespread among the cars on our market and that we see them with better eyes. They are comfortable, efficient and allow us to implement more driving aids.
However, the fact that we interact less with the gearshift does not mean that they are necessarily less maintenance-free or free of mechanical breakdowns. Today we will review the problems of automatic transmissions and their solutions.
- 1 There are many types of automatic transmissions
- 2 Automatic Transmission Problems and Solutions
- 3 What is the solution to the automatic transmission failure?
There are many types of automatic transmissions
Before going into detail, there are many types of automatic transmissions. The most ubiquitous and the ones to which this article largely refers are torque converter transmissions. This system is driven by oil pressure and is the smoothest, as well as being the “all-time” automatic transmission – it has been with us for more than half a century.
On the other hand, and with different problems, there are the dual-clutch automatic transmissions, which have been with us for more than 15 years. Finally, there are robotized manual transmissions, which are, to almost all intents and purposes, a manual transmission without a clutch pedal.
Nor can we forget the continuously variable transmissions, very common in hybrids, but also present in conventional cars – especially in Japanese models. The only common feature among all of them is that they are driven with two pedals, but they have intrinsically different operations. Therefore, we will focus this article on torque converter gearboxes. We will soon devote more space to breakdowns in other types of automatic transmissions.
Automatic Transmission Problems and Solutions
Here are the 10 most common automatic transmission problems, which indicate a problem that should be fixed as soon as possible.
1) Vibrations when accelerating or idling
In this case, 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 engine components such as a dirty EGR or injectors in poor condition, so it is important to isolate the symptoms from other possible faults.
In the case of the gearbox, 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 may be associated with difficulty in shifting gears.
2) Transmission stuck in gear or takes too long to do so.
It is one of the most elusive symptoms of an automatic gearbox failure. The failure can be caused by the electronics, or it can be caused by a degraded ATF fluid, at an incorrect level, or that has lost properties due to time and lack of maintenance. The consequence is an inadequate pressure in the torque converter, by defect or 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 it is due.
3) Shock when changing gears
This problem usually occurs when hot, and also when shifting 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 may be indicated by a fault signal if the car is sufficiently modern.
The valves are integrated into the mechatronics of the gearbox – they are controlled by electronics, but are mechanical components – and troubleshooting would usually require the help of a professional.
4) It 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 is that we have a failure in the oil pump of the gearbox itself. With no oil pressure, the torque converter will not be able to transmit the engine power to the gearbox clutches, and we will literally not be able to move.
It can also be caused by a catastrophic failure of the gearbox, but the symptoms prior to that failure would have been noticeable for thousands of miles – it would not be a sudden and sudden failure.
Another possible cause may be a malfunction in the lever linkage.
5) Gear “slips” when shifting gears
This is one of the most common failure symptoms in an automatic transmission. If you notice excessive slipping when shifting gears, the problem clearly indicates wear in the clutches of the automatic transmission.
This is a dangerous malfunction – just as it is in a manual car – as we can be left with no response from the car when we need it most. It is a malfunction that will increase and end up making driving practically impossible. In some cases, it could be evidence of a problem derived from a low ATF level, but generally, it will be necessary to open the gearbox and change its clutches.
A similar malfunction 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 is coming from the transmission, chances are we have overheated transmission oil. ATF fluid degrades at elevated temperatures and loses lubricating properties.
You can imagine the result: accelerated wear due to excess friction, metal debris inside the gearbox, and all the problems that come with it. Run to the workshop to solve the problem, and drive your car as little as possible if you detect the problem.
A high temperature may be a problem of the gearbox cooling system or an insufficient ATF level.
What is the solution to the automatic transmission failure?
In some cases, a replacement of the automatic transmission fluid may solve the problem and should be the first thing to do before venturing into more swampy waters. If the problem persists, there will be no choice but to disassemble the gearbox from the car and send it to an automatic transmission specialist.
We may be dealing with 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 the conventional use of the car, and in many cars, it may never be necessary.
The failure of an automatic transmission is usually costly and usually requires a transmission specialist.
However, it is an expensive operation with a bill that will run into the four figures. It is therefore very important to change the transmission fluid (and its corresponding filter) when the car’s manual specifies it – or to bring forward its maintenance – and to follow the manufacturer’s recommendations for use.
It is also not a bad idea to treat the car gently: we should especially avoid aggressive driving when cold – something that will be good for the engine, by the way – since the lubrication of the internal components of the gearbox is not optimal at those times.
Hi, I’m Liam. I’m the initiator and writer of this blog. Cars were and will be my first love, and my favorite hobby, that’s why I decided to start this blog and write about my discoveries and techniques to improve my cars or repair them.