How to check an automatic transmission when purchasing

How to check the automatic transmission on a car

Today, an automatic transmission is much more in demand than a traditional manual transmission for a variety of reasons. First of all, the automatic transmission allows you to change gears without driver intervention, which significantly increases comfort and safety.

Taking into account the fact that an automatic transmission is a complex and expensive unit, the cost of a car with such a transmission is, on average, 15-25% higher than a similar model with a manual transmission. It turns out, given the difficult economic situation, not everyone in the CIS is able to buy a new car, especially one with an automatic transmission.

For this reason, when buying a used car, you need to carry out in-depth diagnostics of all components and assemblies, and also know how to check the automatic transmission. Next, we will talk about how to quickly check the machine on a car, which allows you to decide whether it is worth further considering this or that option for purchase.

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How to check the serviceability of the automatic transmission during the initial inspection

Let us immediately note that checking the automatic transmission is the most important step when selecting a used car. A common and widespread mistake is to check only the engine of a used car, assess the condition of the body, identify hidden damage after an accident, etc. At the same time, due attention is not paid to the transmission for one reason or another.

It is important to understand that when buying a used car, the automatic transmission must be carefully checked. The fact is that repairing an automatic transmission may be more expensive than overhauling an internal combustion engine or some types of body work.

Of course, you can immediately go to a service station for diagnostics on every car you like, but in this case, the loss of time and the costs of selecting a suitable option will increase significantly. For this reason, you need to know how to check the automatic transmission right on the spot. So, let's go!

What to pay attention to when talking with a seller

First of all, the service life of the automatic transmission is greatly influenced by the quality of service and operating features. In simple words, you need to understand how the previous owner maintained the machine. There are a few basic questions to ask:

whether the transmission was repaired (if so, why and at what mileage, what was repaired/changed, where the automatic transmission was restored, is there a guarantee for the work);
when was it usually carried out and when was the last oil change in the automatic transmission, and also for what reason (according to regulations and mileage, lubrication condition or other need);
what method was used to change the oil in the automatic transmission (replacement with removal of the pan, partial replacement (refreshing), hardware replacement);
what kind of ATF fluid was poured into the box (original or analogues);
whether the automatic transmission filter was replaced, etc.

It is also important to ask the seller to actually confirm the information he provides (presence of a service book with marks, work orders, certificates of work performed, receipts, etc.).

In cases where the car’s mileage is not high (for example, a car with a “classic” automatic transmission and a real mileage of 120-130 thousand km), and the automatic transmission has not been repaired and has been comprehensively serviced every 50-60 thousand km, then the likelihood of a working condition transmission condition is quite high.

The main thing is that original transmission fluids or high-quality analogues are used, and that the automatic transmission filter is regularly changed. In this case, the wave box may be in good condition and have an acceptable residual life (about 40-50%).

However, if the seller has driven 80-90 thousand km. and just changed the oil before selling (the oil on the dipstick is clean and transparent), or the oil has not been changed and the owner claims that the automatic transmission is not serviced, then this is a reason for a serious check of the automatic transmission on a particular car, a reasonable bargain, or a complete refusal to purchase.

We will also add that you need to ask a question regarding how the car was used. You should pay special attention to indirect signs indicating heavy exploitation. For example, the mileage or age of the car is low, this car has been serviced regularly, but there is a tow bar or marks from it, the general condition of the body, chassis, etc. is cause for criticism.

It is quite possible that such a car was not used for its intended purpose, was actively used in a taxi, for transporting goods, towing a trailer, was driven only on dirt roads, in mountainous or rough terrain, etc. As a rule, obvious or hidden traces of active and aggressive use will reliably indicate that the car has had a “hard” life.

Checking the level and condition of the oil in the automatic transmission

If, after communicating with the seller, no suspicions arose, the owner assures that he changed the oil in the automatic transmission regularly, washed or replaced the automatic filters, did not overload the car, etc., then you can proceed to practical tests of the automatic transmission.

Checks should begin with the ATF transmission fluid. First, it is recommended to drive the car for about 10-15 km so that the oil in the automatic transmission is completely warmed up.
Then you need to put the car on a flat surface, switch the gearbox to P or N mode (depending on the car model), in most cases there is no need to turn off the engine.
Next, you need to open the hood and remove the automatic transmission oil dipstick, wipe it with a clean, lint-free cloth and insert it back. Then the probe is removed again.
First of all, pay attention to the oil level (normal, not lower than the middle between the HOT and COLD marks, but not higher than HOT). Also, no traces of foaming of the automatic transmission oil should be visible on the dipstick.
Let’s also add that on some car models with automatic transmission there is no transmission dipstick. In this case, you need to be prepared for the fact that you will need to slightly unscrew one of the drain plugs (it is better to study the manual separately), and then check the oil.

Checking the quality of automatic transmission while driving

After checking the oil, you need to move on to assessing how the automatic transmission changes gears, how the modes work when the car is stationary, and also how the automatic transmission behaves while driving under different loads.
- To check, the box needs to be warmed up, then the car should be stopped, press the brake and start switching different modes using the selector lever. At first, you should switch slowly, staying in each mode for 10 seconds. Further switching should be performed faster (1 second in each mode).
- In this case, you need to pay attention to whether there are any obvious delays and failures when switching modes, extraneous noise, vibrations, and also whether there are strong shocks or jerks when changing from one mode to another.
- It is also important to understand that there should be minor jolts; this is the norm, indicating that modes and gears are being engaged. The strongest shock will be when the selector switches from mode “D” to “R” and vice versa. However, there should not be any jerks or vibrations when the entire car is pushed or shakes.
- The next step is to check the machine while driving. All tests are performed on a warm engine and automatic transmission. It is optimal to immediately find a flat, long stretch of road for testing, where you can actively accelerate and brake.
Afterwards you need to perform a smooth acceleration to 30-40 km/h, followed by sharp acceleration (kick-down mode is triggered). You also need to first accelerate, then release the gas pedal and do not press the brake so that the car slows down with the engine.

Next, smooth braking is applied using the brake pedal until a complete stop, and then emergency braking. Such actions are necessary to assess the quality of the downshift.

In this case, no jerks, strong shocks, vibrations, delays during switching, automatic transmission slipping, etc. are allowed. The gearbox must engage all gears clearly and in a timely manner. If the machine malfunctions, this directly indicates its malfunction.

With a sharp start and acceleration, the car should accelerate much more actively, while the speed can reach 5 - 6 thousand. The dynamics of acceleration should be close to the indicator indicated by the car manufacturer itself. For example, if a car with an automatic transmission, according to its passport, must accelerate to “hundreds” in 10 seconds, then the acceleration dynamics should be close to this mark.

If the driver presses on the gas, but the car does not accelerate or the acceleration is very slow, and the engine speed is high, this indicates that the automatic transmission is slipping (the clutches are slipping). A test for downshifting during braking or rolling is also highly recommended, since in some cases it is during downshifts that malfunctions in the automatic transmission can be noticed.

Another option for checking a hydromechanical automatic transmission is to park the car with its nose up (driving uphill). After this, the driver releases the brake pedal, but does not press the gas. If the slope is not too steep, the machine will move forward slowly or stand still. Rollback is not allowed for boxes of this type.
- Let us add that in some cases it is still possible to carry out the so-called Stall speed Test (Stall-Test automatic transmission, Stall-Test automatic transmission). Please note that such a test is not recommended unless absolutely necessary!
You should also be sure to notify the seller in advance of your desire to carry out such a check, and to make it known that there are certain risks, possible breakdowns or subsequent disruptions in the operation of the automatic transmission.

As a rule, a gearbox that is already worn out, but still works relatively normally, after the test may begin to slip a lot, automatic transmission errors light up, etc. In short, to carry out the test, the driver presses the brake, while without releasing the brake pedal, switches the transmission to mode D and simultaneously presses the gas all the way. In this case, the gas pedal cannot be held down for more than 3-5 seconds.

After the check has been completed, you need to release the gas pedal, the brake is not released, and the gear shift lever is moved to N. The engine idles for 3-5 minutes, the oil in the automatic transmission cools during this time. Then the check is carried out in a similar way in other automatic transmission modes (except P and N)

If the speed is noticeably higher, you should immediately release the gas, since an increase in speed indicates slipping of the automatic transmission in the clutch packs. If the speed is lower, this may indicate a malfunction of the automatic transmission torque converter. In the case where the stall speed value is within the normal range, it is generally accepted that the gas turbine engine, clutches and engine are operating normally.

What's the result?

As you can see, there are several simple and accessible methods that allow you to pre-check the automatic transmission when buying a used car right on the spot. If the operation of the transmission and the condition of the oil in the automatic transmission do not cause any comments, then you can safely go to the service station, and you should not neglect professional and complete diagnostics of the car at the service center.

If necessary, car service employees separately draw the buyer’s attention to the presence of extraneous sounds during the operation of units and components, point out parts that need to be changed soon, etc. As a result, the identification of certain malfunctions and defects can become a serious basis for reasoned bargaining or a complete refusal to purchase a specific used car.

Why the automatic transmission kicks, the automatic transmission jerks when changing gears, jerks, jerks and impacts occur in the automatic transmission: the main reasons.

Automatic transmission slipping when changing gears: the main reasons why an automatic transmission slips. Box diagnostics, troubleshooting.

What is automatic transmission emergency mode? Why does the automatic transmission go into emergency mode: the reasons why the automatic transmission goes into emergency mode, diagnostics.

A jolt in the automatic transmission, the appearance of jerks when shifting gears of the automatic transmission, jolts of the automatic transmission in place: the main reasons for such malfunctions of the automatic transmission.

How to determine that the automatic transmission is overheating: signs indicating overheating of the automatic transmission. How to improve automatic transmission cooling and prevent the machine from overheating.

Checking the oil level in an automatic transmission: how to check the ATF level. What else to pay attention to: color, smell, ATP contamination, etc.

How to check the automatic transmission when buying a car? Proper automatic transmission check is the key to a successful car purchase

Every time you decide to make a particular purchase, you will face certain difficulties. In the case of choosing a car, the difficulties are mainly related to the choice of brand, model, engine type, color, as well as gearbox type. Regarding the latter, on the pages Question Auto we have already raised the topic “Which is better, automatic or manual,” so today we will talk about something a little different.

Today we will try to help those who prefer the automatic transmission option, and we will tell you how to check the automatic transmission when buying a car, so as not to regret your purchase later. Everything needs to be checked, from the body and interior to the engine and gearbox. However, these are very extensive topics, so today we will only consider automatic transmissions.

In the case of a manual transmission, the check comes down to a banal test for smooth shifting, both on the spot and while driving. In addition, it is necessary to check the oil that is poured into the box (smell and color), and also listen for any extraneous noise, knocking and other sounds unusual for the gearbox.

As for the automatic transmission (automatic gearbox), everything is much more complicated with it, which is probably why there are fewer people willing to buy a used car with an automatic transmission than similar cars with a manual transmission. People are afraid to get into trouble and “buy a repair” instead of a car. In addition , few people know how to check the automatic transmission or understand that the “automatic” is slowly dying. The fear is not unfounded, since repairing an automatic transmission is not cheap, and there are only a few people capable of performing it flawlessly. The whole reason is that a modern automatic transmission has a rather complex design and there are not so many people who want to “tinker” with it; it is easier to repair several manual transmissions than one “automatic” and earn many times more.

With normal operation and compliance with all its rules, an automatic transmission can serve for decades with truth and faith. However, you only have to “give the box some trouble” once, for example, get stuck in the mud or skid in the snow for 15-20 minutes, and the automatic gearbox will receive such wear and tear that repairs are out of the question.

The most annoying thing about this issue is that even after repairing the automatic transmission, its performance may be in question; or rather, it will work, but not as well as before. The fact is that at the factory, automatic transmissions are assembled with such precision and scrupulousness that it is almost impossible to achieve similar quality outside the factory; accordingly, both repairs and further operation of the box will be far from ideal. The slightest grain of sand or a piece of metal shavings that was not seen by the specialist performing the repair can lead to a repeat breakdown and the need to repeat expensive repairs.

Considering the above, we can conclude that buying a car with an automatic transmission and checking the automatic transmission when buying a car is a very important and responsible step that must be taken seriously.

How to check the automatic transmission?

1. The first thing you need to find out is how and where the car was used, how many owners the car had, and what was put into the box. If the car is brought for sale from Europe, this is already good; as a rule, motorists abroad are serviced by dealers who make the appropriate notes in the service book. Refuse to buy immediately if the owner tells you that: “The car was in an accident, but after that the car was allegedly repaired and now it is even better than before the accident. “The same goes for cars that were in a taxi; I don’t recommend taking a “taxi driver’s” car, because we all know what loads these cars receive.

2. If you saw a towbar from behind, you know that the car was “dragging” something, but what and how much is the third question. Trailers and other towed devices negatively affect the transmission and engine, and especially on cars with automatic transmission.

3. Check the oil level, color and smell. The automatic transmission is filled with ATF oil, which is usually red in color. The level is checked on a flat surface, the gear selector should be in the “N” position, in some cars in the “P” position. The level should be between the “HOT” and “COOL” marks. If the smell of the oil contains signs of burnt or other foreign odors not characteristic of oil, I strongly do not recommend you buy this car. A slight change in the color of the oil from red to light brown is allowed, provided that the box is working properly and there are no metallic inclusions in the oil itself, which can be easily detected with a white sheet of paper. Apply a few drops of oil to the sheet and look closely to see if there are any black or gray metal dust particles, shavings, etc. on the white background of the sheet.

4. Next, you need to check the smoothness and correctness of gear shifting. We warm up the engine and try to switch the automatic transmission operating modes. When switching, you must depress the brake, do not forget about this! When switching modes, you should not feel too noticeable jolts or jerks of the car or the selector. Delays in shifting, jolts, clicks or impacts during shifting are a clear sign of incorrect transmission operation. The only jerk that is considered normal is a small jerk when switching the selector to “D” mode. Although it is very difficult to give any specific advice on this issue, since “automatic” and “automatic” are different! Some more modern models operate inaudibly and there shouldn’t be any jerks, on the other hand, older automatic transmission models had these very jerks, and when the “D” or “R” mode was turned on, a slight vibration was felt, this is considered the norm, again - same as for which box. In general, your task is to find an option that will have a minimum of all these “phenomena”, and ideally, none at all.

5. If the machine has passed all the tests described above, we move on and offer the seller a ride in the car to make a final decision. Some sellers do not allow you to drive until you have purchased the car. They can be understood, because if you have an accident during a trip or someone hits you during a test drive, it will be very difficult to present anything to you. Therefore, we are not upset and ask the owner to follow the commands that you will give him during the test drive.

It is necessary to check all modes in all possible situations, namely:
- A sharp increase in speed from a standstill. Acceleration should be rapid, without jerking or knocking.
- Sharp acceleration while driving (while driving, for example, in 4th, after sharply pressing the gas pedal, the box should switch to a lower gear, that is, 3rd, 2nd or even 1st gear, depending on the what kind of box is installed).
- Sharp braking. The “automatic” should reset all speeds to 1st without delays or jerks.
- Watch the switching, up to 60 km/h the automatic transmission should switch at least twice from 1st to 2nd, from 2nd to 3rd. Make sure that when changing gears there are no jerks, especially from 1st to 2nd (although almost all automatic transmissions have them, only the most advanced automatic transmissions and, of course, the CVT will not have jerks).
- The problem with many automatic transmissions is slipping; it is very difficult for an inexperienced car owner to notice, but this will be indicated by the gas pedal and engine speed. Slipping is the moment when the speed increases and the pedal goes down, but the car does not go faster. This means that the clutches inside the automatic transmission are already worn out or there is another malfunction that does not allow the automatic transmission to function adequately.
In general, I will tell you as the owner of a car with an automatic transmission, while driving you should not feel anything that could alert you. With ideal and coordinated operation of the engine-automatic tandem, the operation of both should be almost inaudible. The only moment when you should feel the loud operation of the engine and a rapid, growing jerk forward is during intense acceleration, at which point the “purring” engine and smooth automatic transmission turn into a wild tiger, which can even growl depending on the engine power and “sharpening” the car itself. If the car is “sports” (why I put the word “sports” in quotation marks, because sports and automatic transmission are incompatible things). For example, Honda Accord Type S, then growling at high speeds is normal. The most important thing is that the jerks are not short and intermittent; the jerk should be felt from acceleration and pressing hard on the gas, but not from the fact that you are accelerating evenly, while the car jerks as if an anchor is attached to it, which constantly clings and slows down the car. I think the example is clear to you, and you can easily distinguish a working machine from a faulty one.

If you still doubt the correctness of your verdict, invite the owner to visit the dealer for service, ask them to check the automatic transmission in full; if the “automatic” has any malfunctions, then they will certainly be detected during diagnostics.

How to check the automatic transmission when buying a used car? (step by step instructions with video)

Good afternoon. As you may have guessed from the title, in this article I will tell you how to check the automatic transmission when buying a used car. The article is a video and its text description.

The first check of the automatic transmission is the Stall speed Test.

This is the most universal test that shows the general condition of an automatic transmission. This test allows you to determine the wear of the clutches in the box, as well as the condition of the oil and donut (torque converter).

The test procedure is as follows:
- We warm up the engine and gearbox, for this we drive 10 - 15 km.
- We place the car on a horizontal platform.
- With your left foot, press the brake pedal all the way.
- Move the automatic transmission selector to position D (drive).
- With our right foot, we sharply press the gas pedal to the floor for five seconds, while looking at the tachometer, we are interested in the maximum speed that will be achieved by the engine (as soon as the speed has stopped increasing, the test can be stopped).
In no case should you hold the car with the brake in gas to floor mode for more than 5 seconds, since the gearbox is working in heavy duty at this time.

For most cars, when performing a stop test, the speed will be set in the range from 2000 to 3000. Moreover, the transmissions of 70% of cars are designed so that the speed test shows 2200 revolutions.

If, as a result of the test, the engine does not spin up more than 2000 rpm, then the engine itself is probably faulty - it is not developing full power.

If the engine does not spin above 1500 rpm, the automatic transmission “donut” is probably faulty, or the oil in the box has not been changed for a very long time.

If the engine speed exceeds 3000, the clutches of the automatic transmission are probably faulty, and it is living its last days.

In any case, a car that does not pass this test well is not worth purchasing.

Exceptions to this test are tuning cars. Some companies specially modify the automatic transmission donut so as to increase the maximum speed, this is done for more intense acceleration, but has a negative impact on the service life of the transmission. Personally, I highly doubt that a person who buys tuning cars will read this article.

The second check is the start of movement.

The check is carried out as follows - we stop the car on a horizontal section of the road, press the brake, put the selector in position D, release the brake, while not touching the gas pedal, as a result the car should start moving. We do exactly the same check in position R (reverse).

If the car starts to move, this indicates wear on the clutches in the gearbox; replacing them is expensive.

The third check is acceleration and braking.

The verification method is as follows: we start driving by pressing the gas pedal by about 30%, while the car should slowly and without bumps or jerks pick up speed. In this mode, it is advisable to wait for all gears to shift sequentially.

After waiting for the last gear to engage, we also smoothly stop the car by coasting, and all gears should sequentially engage in the opposite direction.

The next check is carried out according to exactly the same scheme, only the gas pedal should be pressed two-thirds. In this case, acceleration is carried out with greater intensity. In this case, there should not be strong kicks, but transmission shifts can be felt.

The fourth check is a kickdown.

This check is carried out as follows: the car is moving at a speed of 70-90 km/h, the gas pedal is pressed sharply, until it hits the floor.

The automatic transmission should drop one or two gears down, that is, switch to third or fourth gear, the engine speed should increase sharply, and at the same time intense acceleration should begin.

The fifth check is checking the oil.

If the car is equipped with a service dipstick, take it out, check the oil level; it should be between the minimum and maximum marks depending on the temperature: on cold, 25 degrees, respectively, on hot, 80. We look at the oil; there should be no crumbs in it and there should be no smell from it burning.

The sixth check is checking for oil leaks.

The last check of the gearbox is carried out under the car in a pit - we inspect the box from below for leaks of gaskets, seals and plugs.

This is where checking the automatic transmission ends; check without opening anything else.

To illustrate how the automatic transmission is checked, I recorded this video:

It is important to understand that automatic transmission malfunctions are usually very expensive to fix, and in most cases are solved by replacing the automatic transmission with a contract one. Therefore, if you have any doubts about the serviceability of the box, it is better to refuse to buy a car, or ask for a discount on a contract box.

That's all for me today. I hope that you understand how the automatic transmission on a car is checked. Smooth roads and reliable transmissions to everyone. If you have any questions, ask in the comments….

How to check the automatic transmission before buying a car. #10

Part 9 of the large guide “ How to choose and check a used car before buying .” Links to other parts are at the bottom of the article.

Attention! At the bottom of the post is a video version of the article. The article completely repeats the text material of the video, but the video contains more illustrations.

By analogy with checking the engine, checking the gearbox should be completely cooled after operation and before it is completely warmed up, since many sores, especially in their infancy, appear precisely “cold” until the gearbox is warmed up, and some, on the contrary, only “ hot."

Start by visually inspecting the gearbox itself for leaking gaskets and seals. Inspect the box from above in the engine compartment, and also try to look from below. Ideally, the entire box should be dry on all sides, without oil fogging and transmission oil leaks. If the automatic transmission pan gasket “sweats,” then you can get away with the cost of replacing the transmission oil and gasket, but if a leak is found at the main oil seal, at the junction of the engine and gearbox, the problem may be more serious than at first glance.

Exhausted oil (ATF fluid) thickens and loses its working properties, therefore, especially during a cold start, the automatic transmission operates with oil starvation, which can lead to the torque converter bushing oil seal being squeezed out of the pump housing.

This causes a leak in the area where the engine and automatic transmission meet, which entails expensive repairs that involve removing the transmission. The problem may also be in the rear crankshaft oil seal of the engine.

If the box has a dipstick or plug that allows access to the oil, check the oil level and quality. This is a very important part of diagnosis. The oil should not be black, too thick, have no abrasive inclusions or have a burning smell. The normal operating color of transmission oil is red to light brown.

A burning smell may indicate that the friction disc linings are burnt. Without going into details that are unnecessary for “street diagnostics,” you can compare groups of friction discs in an automatic transmission with the clutch on a manual gearbox; they perform approximately the same role.

When changing gear in an automatic transmission, one group of friction discs opens, ceasing to transmit torque, and the other group contracts, and another gear is engaged. Loss of pressure in the automatic transmission due to thickened oil, insufficient oil level or faulty solenoids leads to underpressure of the clutches and their increased friction. If we draw an analogy with a manual transmission, this is approximately the same as constantly driving with the clutch half-pressed - the clutch burns out.

Due to increased friction and insufficient cooling, friction linings, most often made of cellulose, begin to char. This starts an irreversible process of failure of the automatic transmission, causing critical harm to the quality of the transmission oil itself when the friction temperature reaches the flash point of the oil. This is where the burning smell of transmission oil appears.

Charred friction linings do not absorb enough oil for cooling and begin to deteriorate, especially since the burnt oil no longer fully performs its functions. The destroyed parts of the clutches and their adhesive base are carried along the narrow channels of the automatic transmission, clogging them, which again reduces the permeability of the channels for transmission oil and further aggravates the problem.

At first, slipping of the friction discs manifests itself in the same way as slipping of the clutch on a manual transmission - when you pick up speed in a gear, but the car does not pick up speed. Torque is not transmitted from the engine to the wheels. In a neglected state, the abrasive from destroyed friction linings is spread throughout the entire transmission, creating increased production of all its components, which can lead to major repairs or replacement of the automatic transmission.

In addition, replacing burnt oil with a new one may not solve the problem at all, but only make it worse. New, liquid oil, replacing the thick liquid, with its cleaning properties will help peel off damaged friction linings, which will further clog the valve body channels and filter, and the burnt clutches themselves will begin to slip even more readily.

I think you already understand how important the role of transmission oil is and how important it is to check its level and condition. I repeat, if the quality of the oil causes serious concern, foreign inclusions are found in it, it is black and has a burning smell - do not consider this car for purchase.

Get behind the wheel of the car and, holding the brake pedal, check the operation of all automatic transmission modes, simply switching them from mode P (park) to mode R (reverse), D (drive) and back. Try shifting slowly and then quickly. A slight jolt may be felt when shifting. Exactly easy! But if light shocks have already become blows or very noticeable kicks, then this can be the cause of a number of problems - from the banal need to change the transmission oil and filter, to more serious ones that require expensive repairs.

But if the quality control of the oil shows its satisfactory condition, then most likely the problem of “shocks” of the box cannot be solved simply by changing the oil. Perhaps the car owner has already changed the oil with the hope that this will solve the problem with the transmission kicking, but this did not help, which was the reason for selling the car.

If you feel a strong vibration when the Drive mode is on, then the problem may not necessarily lie in the gearbox itself. And the cause may be partial or complete wear of the engine mounts or gearbox mounts. It would seem that the problem is not big, but replacing pillows can significantly tug at your pocket.

The appearance of vibration when the car is moving at a speed of 50 km/h or more may be a symptom of a malfunction of the torque converter (GDT). Other gas turbine engine malfunctions may manifest themselves as slipping of the box when starting to move, loss of vehicle acceleration dynamics due to a malfunction of the overrunning clutch, or extraneous sounds when the vehicle is operating.

Mechanical noise when changing gears, which disappears with increasing vehicle speed, or a rustling sound when the vehicle is running, may indicate problems with various bearings of the gas turbine engine. If the car stalls when changing gears or operating modes, this is also due to the torque converter, and most likely its control electronics. The torque converter is the key link that transmits torque from the engine to the automatic transmission; in fact, it is an analogue of the clutch.

Be sure to check the operation of the automatic transmission while driving. Check all operating modes - reverse, very slow acceleration, normal acceleration, intensive acceleration (“slippers to the floor”), holding high speed and resetting speed, that is, changing gears from the highest to the first, simply by releasing the accelerator pedal. A working automatic machine in all modes should work without twitching or failure when accelerating, and also without long delays, extraneous sounds, strong shocks and, especially, without noticeable shocks when changing gears.

It is important to perform this check - accelerate, release the gas, continue accelerating, sharply reduce speed by braking, then start accelerating again. Again, there should be no twitching or dips. There are symptoms that appear in this mode and, as a rule, this indicates problems with the valve body or automatic transmission solenoid valves (solenoids).

During intensive acceleration, pay attention to the ratio of the intensity of the increase in speed and the increase in speed - the speed and speed should increase proportionally. If the speed increases rapidly, but the acceleration lags behind, perhaps worn or undercompressed friction discs, which should be tightly compressed, are slipping, in other words, the machine is slipping. Of course, if your goal is to purchase a working car, this option is not suitable for you. Activation of the Drive, Reverese mode, as well as gear shifting while moving should occur without noticeable delays, otherwise one may suspect that the solenoid, plunger or pistons compressing the friction discs are jammed.

The reason for strong automatic transmission jolts, which is often called “the box kicks,” when the Drive, Reverse modes are turned on, or when changing gears while moving, can be caused by incorrectly functioning clutches, solenoids, plungers, valve body and other associated parts. Most often, the problem in their operation is caused by clogging and wear, which causes jamming. Untimely oil change (ATF fluid) is most often the root of all problems and triggers irreversible processes of increased wear of almost all parts of the automatic transmission.

A solenoid in an automatic transmission is an electromechanical valve that, in response to an electrical impulse from the electronic control unit of the automatic transmission, opens or closes channels in the valve body, thus controlling the flow of transmission oil (ATF fluid). Different solenoids open some and close other channels, so the pressure is transmitted to the corresponding pistons, which compress or decompress different groups of friction discs responsible for different gears - this is how gears change.

Also check the speed reduction by braking to a complete stop; the speed should not sag much and, moreover, the engine should not stall, which may indicate a malfunction of the torque converter, the so-called donut. I mentioned it above.

For a test drive, choose a suitable road where you can accelerate enough to check that all the automatic gears are engaged. After all, an automatic transmission may not slip or kick in all gears, but only in those whose corresponding solenoids and clutch groups are faulty. Some gears may not be engaged at all, which is a reason to simply count the number of all shifts from first to maximum gear.

Of course, the cause of strong transmission jolts can be not only the solenoids or clutches themselves, but when choosing a car, the presence of these negative symptoms is enough for us to refuse the purchase.

Automatic transmission diagnostics: what, where, when

Modern cars have a transmission unit in their structure and design. If it is automatic, then this node is considered complex. With a manual gearbox everything is much simpler: the clutch does not work, I took it apart and replaced it. Specially trained people can work on automatic transmissions for repairs and maintenance. But all drivers of cars with an automatic transmission need to know the symptoms of certain transmission problems and be able to diagnose it with their own hands, so to speak.

When and how to diagnose an automatic transmission

The benefit of initial detection of problems at the first sign of incorrect automatic transmission operation is enormous. If you immediately identify the cause of incorrect operation, you can avoid expensive repairs and not have to stand idle during repairs.

Of course, if you decide to buy a used car, then you need to check all the components and pay attention to small details, such as, for example:
- Is there a tow bar? Yes, yeah, that means I was driving under load. And an automatic transmission, be it a robot or a CVT, can suffer greatly if it is operated under load, that is, with a loaded trailer.
- What a mileage. If about one hundred thousand and have never changed the oil filter in the automatic transmission and the oil itself, then there is a possibility that the parts in the unit are operating in wear mode.
If the oil has been changed and there is no towbar, then you still need to diagnose the automatic transmission.

The initial check of an automatic transmission includes well-known procedures:
- Check the oil level in the box.
- Check how clean the oil is: transparent and not curdled or thickened, cloudy.
- Check control cable adjustment.
- Check STALL TEST.
- Check how the gearbox switches while driving.
Now in more detail how to complete the above steps.

To check the transmission fluid, then oil, you need to learn how to check the level and its quality. The level is usually checked using a dipstick, which has special marks. However, there are boxes without a dipstick.

American automatic transmissions have a dipstick for checking the oil level, but European ones usually do not. How to check the oil level in an automatic transmission if there is no dipstick? The answer is simple: if there is no dipstick, oil was added from somewhere, then there is a plug. Oil is poured into such boxes to the level of the hole. This means you need to unscrew the plug, the level of this hole will be the mark for the correct filling of fresh transmission oil for the automatic transmission. Regardless of whether there is a dipstick or not, the oil level is checked to ensure that the oil in the box is warm. To heat the oil in the box to operating temperature, which is about 90 degrees, you need to drive 13 kilometers. After that, we put the car in a level position. If there is a dipstick, then everything is simple: pull the dipstick out, wipe it with a clean napkin, put it in again, stick it out again and see how far the dipstick sinks into the oil. Usually there are marks HOT (hot) - the upper level and there is a lower mark COLD (cold - cold), when the oil level should be cold. If the oil level does not exceed the upper mark and is not lower than the lower mark, then there is a normal amount of oil in the automatic transmission.

If there is no dipstick, you will have to drive into a hole or overpass, unscrew the plug and check the level with a clean wire or stick. As we said, the level in such automatic transmissions should be up to the hole itself.

If metal shavings are visible when checking the oil, this means that the parts working in pairs are touching each other and wear is occurring. In this case, a more in-depth check is required at a specialized car service center.

How to check the oil level if the automatic transmission does not have a dipstick and there is no oil filler plug?

Yes, yes, there are such boxes, who doesn’t know. This is a box with code 722.6 from Mercedes, five-speed automatic. The answer is also simple: there is no need to check the level in such a box. The fact is that German engineers came up with the idea of separating the cavity with oil from the working pan. A bypass valve is mounted between them, which maintains the optimal required level.

Checking the automatic transmission adjustment cable

Here again, the condition of the cable is affected by the mileage. The cable can gradually lengthen by microns or millimeters, like a timing chain.

In what cases is it necessary to adjust the automatic transmission cable?

If while driving you notice that the car shifts too late or too early, you need to adjust the cable. If you use an automatic transmission for a long time with an unadjusted cable, the automatic transmission will quickly wear out.

Checking the automatic transmission - parking brake (stall test)

Testing will show how the torque converter (GDT) of the box works. This diagnostic step should only be carried out by an experienced automatic transmission specialist, otherwise you may, on the contrary, break the parts.

The principle of checking Stall Test (steel test) is as follows:
- drive several kilometers to warm up the transmission oil in the automatic transmission;
- stop the car so that there is plenty of free space in front and behind it in case the brakes are weak;
- turn on the handbrake;
- sit behind the wheel, press the brake pedal all the way with your left foot;
- move the box to position “D” (drive - movement);
- With your right foot, sharply press the gas pedal all the way and hold it for no more than five seconds (the less, the better).
Immediately after this procedure, you cannot repeat it; you must wait ten or fifteen minutes for the oil in the automatic transmission to cool down.

This test will show how the friction discs work and the operation of the torque converter in general. After checking, the gearbox handle must be moved to position N (neutral) and let the engine run for several minutes so that the oil in the automatic transmission cools down.

The fact is that such a check is recommended to be done by the manufacturers of automatic transmissions for cars.

Vehicle behavior when diagnosing with the parking brake:
1. The brakes hold and squeak, but the car barely crawls. Indicates that the brake system is faulty.
2. The effect of engine tripping, that is, the car shakes. This means there is a problem with the ignition system, which means that if it is not corrected, the car’s engine will operate with reduced power. Solution: check the spark plugs, high-voltage spark plug wires, spark plug tips.
3. When carrying out diagnostics using a parking test, a working automatic transmission should allow the engine speed to rise in one second to about 2800 rpm for gasoline internal combustion engines; for diesel engines with a working automatic transmission, the number of revolutions per second will be 2000 rpm.
These are indicative figures. Such diagnostics should be carried out by a specialist who knows what parameters and for what time the unit should show when checking the stall test.

How to check the automatic transmission while driving

In a normally operating automatic transmission, some jolts are allowed when switching to cold. When warm, there should be no shocks.

During acceleration, increasing gears, as well as when slowing down, downshifting should be smooth, without jerking or slipping of the automatic transmission.

There are also simple diagnostics that every driver can do. The idea is to stop the vehicle on an incline and take your foot off the brake pedal. If the car goes backwards, then there is a problem with the automatic transmission.

If slipping, jerking, impacts, noises were noticed during the trip, then the reason may be a breakdown of the freewheel, wear of the clutches, etc.

Recommendations

If diagnostics have shown problems with the automatic transmission system of a used car that you want to buy, then it is better to abandon this option, because an automatic transmission is a complex device that must work like an accurate clock. Bringing it close to factory condition is not an easy task.

Service center specialists immediately identify which part has a breakdown: electrical, hydraulic or mechanical. ATF transmission fluid is even checked for smell, color and what its pressure is in the system.

It is advisable to choose a used car, either with an automatic transmission or a manual transmission, with a knowledgeable specialist. For example, an acquaintance went to the car market to choose, take with him an engine specialist, who immediately said that the compression was not what was needed - they measured it, yes, it turned out that the engine really had a lot of wear.

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