Automatic transmission does not respond to gear changes

At some point you realized that the gearbox does not change gears, we will try to figure out the reason. The complex device does not allow you to immediately understand why the automatic transmission does not change gears. The reasons can determine the signs that reflect the behavior of the machine. The most correct and common cause of gearbox failure was the driver. Unprofessional use of the car leads to the fact that sooner or later something breaks. The car has become in demand and useful, not everyone will climb under the hood to check the degree of wear of a particular part in order to prevent breakdown before it occurs.

Lack of transmission fluid

Let's take a closer look at several problems that arise when there is a lack of transmission fluid.

The car does not move and a jolt is felt when the lever is shifted. The main reasons lie in low oil level. The situation can only be corrected by replenishing fluid, perhaps even cleaning the canals.
The automatic transmission does not change gears when going uphill, the gear is downgraded, and the car starts slipping. The higher mode does not turn on. Low fluid levels reduce the vehicle's performance. At the same time, it is worth paying attention to the components (seals, couplings, cuffs) - their condition and degree of wear are significantly reflected in gear shifting. More often than not, the only solution is to change the oil and add fluid.
Clutch slipping when changing the position of the lever on the gearbox indicates problems in the valve body; the reasons may also be hidden in the filter. In this case, it is worth assessing the fluid level and cleaning the filters.

If the automatic transmission does not change gears, the car is constantly slipping, the oil turns into foam with a change in color, then it is worth checking for the presence of water in the gearbox. Liquid ingress negatively affects the functionality of the automatic transmission and foam forms. The second reason why gears do not change when the car behaves like this is clogging of the valve body valves. The technicians will help you disassemble the mechanism and check how the pumps attached to the block work.

Friction disc wear

When changing gear into an automatic transmission from reverse gear, the car begins to slip. The reasons for the machine's behavior are hidden in:

displacement or deformation of friction discs;
rupture of rings or couplings;
valve sticking.

Disc wear can also affect the performance of the transmission. For example, it is impossible to switch to reverse gear, while at the same time moving forward is only possible in second. The reason for this behavior of the car lies in the wear of components; rubber parts are easily worn out when driving. If, during visual diagnostics, all of the specified parts are intact, then further attention should be paid to the clutch drum; perhaps the reason lies there.

You won't be able to drive a car when it's cold. If, when warming up, the car slips at forward and reverse speeds, then you should pay attention to the properties of the oil used, and if possible, it should be replaced. In addition, there may be another reason for this behavior of the car - a clogged filter.

When starting to move, the car slips in place, the movement itself continues, the speed switches perfectly. This may also indicate wear on the friction discs. In this situation, attention should be paid, among other things, to the condition of the torque converter (hub wear is possible) and to the piston cuffs.

The gearbox does not respond to shifting

The hardest thing is when not a single gear shifts completely in the gearbox, either in automatic or manual modes, and there is no push that accompanies the switching. There may be several reasons for this behavior of the car:

valve body malfunction;
lack of transmission fluid;
breakdown of the pump drive gear;
gear shift valve sticking;
brake band wear;
wear of friction discs.

How does the automatic transmission work?

In order for the transmission to work properly and not delay acceleration, you need to understand that an automatic transmission is a more complex unit in design compared to a manual transmission.

It includes several important elements:

planetary system with a set of speeds, responsible for the transition between automatic transmission stages;
a torque converter that acts as a clutch and transmits torque to the wheels;
clutches and mechanisms that provide transition between gears;
valve body - electronic control unit.

The main medium and driving force in an automatic transmission is the transmission fluid - oil. It is supplied under pressure to the torque converter blades, thereby causing the wheels to spin. The pressure with which the liquid presses on the mechanisms depends on the choice of stage.

Actions of motorists

I’m moving on to the most anticipated part - if you are not able to figure out on your own why the gear shift on your gearbox does not engage, then you should contact a car service center, where specialists will carry out diagnostics and educate you about the breakdown, cost and repair time. Checking the functionality of automatic gearboxes is carried out only using computer diagnostics, so you should make sure that the service is available at the car service center.

If after diagnostics no faults are found, and the car continues to act up when changing gears, then you should pay attention to the speed sensors, wiring and scenes.

The backstage can be cleaned quite easily using a hole in the garage or an overpass. The gear and speed sensor is a rather capricious thing. If there is a breakdown, the sensor stops sending signals, which forces the gearbox not to respond to the signals (the gearbox simply sees that there were no signals).

If all the presented methods for eliminating the breakdown are not effective, then the car requires the intervention of a car service guru.

It is worth understanding that there are many more causes of failure, symptoms and methods for eliminating them. You should not delay resolving the issue and allow your car to “cure.”

The box has a rather complex structure, and it is impossible to answer this question right away. But based on some indirect signs, you can determine the essence of the problem and try to fix it yourself.

Problems associated with a lack of transmission fluid

1. When you move the shift lever to any of the positions, a push is felt, but the car does not move either forward or backward. A low oil level can occur due to leaks, a faulty torque converter, or a dirty oil filter. Treatment methods are obvious: replace, fix, clean. And be sure to add fluid to the level.

2. On an automatic transmission, gear shifting in the highest mode during a long climb causes slippage and a premature transition to a lower gear. This occurs because insufficient fluid level reduces hydraulic forces. The cause may also be wear of the clutch discs, wear of the cuffs or o-rings. Replacement and topping up help solve the problem.

What you can do with your own hands

There are a number of simple actions that can prevent the automatic transmission from stalling.

Reasons why the transmission delays the transition between stages	Troubleshooting Methods
Automatic transmission overheating	Lack of transmission oil level, heavy loads on the automatic transmission;
Wear and destruction of internal mechanisms	Clean the magnet, change filters;
Sensor malfunction	Replace them, preferably with original ones

Servicing a car when the automatic transmission is delayed in transmission does not always mean many problems. Some automatic transmissions are capable of exceeding the 500 thousand km mark without major repairs. To check the transmission for gear drag, it is recommended to turn on the kickdown mode. Its name describes the moment itself: push down.

If, while driving a car with automatic transmission, you sharply press the gas pedal, the car goes to a lower gear so that the speed increases as quickly as possible. If this moment passes quickly and without interruptions, then the box does not delay transitions and is in good working order.

Read

How to remove and install automatic transmission

The simplest actions that any car enthusiast can perform for his favorite iron horse when tightening is to change the oil filter and the “transmission” itself in the automatic transmission. But you need to buy consumables in trusted places so as not to stumble upon a fake.

Problems associated with friction disc wear

• Reverse gear on an automatic transmission is engaged without any complaints, and when the lever is switched to forward, the car slips in place. In addition to wear of the friction discs, breakage of the cuff or breakage of the direct clutch rings, the problem may be a stuck valve in the valve body.

• Move forward only at speed no higher than second, there is no backward movement. Disc wear affects. The problem may also be a breakage (wear) of the piston seals or breakage (wear) of the clutch oil sealing rings. If everything is in order here, pay attention to the clutch drum: the spline joint may be cut off or otherwise damaged.

• After the oil warms up, slipping is observed when moving both forward and backward. This phenomenon occurs when the viscosity of the oil decreases when heated, and the worn discs are not pressed so tightly against each other. Friction dust, a product of disc wear, may also be the cause. It clogs the filter mesh, causing the main pressure to drop.

Melting of friction discs due to high temperature

The clutches in the machine control the movement of the shaft and gear. They narrow or widen, slowing down or releasing the automatic transmission gears. Due to insufficient pressure, the discs do not narrow to the required size. This promotes rotation of the shaft and increased friction of the machine elements. The temperature rises and the oil may burn.

As a result, the clutches wear out, which leads to free running of the gears. This interferes with the smooth running of the vehicle. There is only one way out - replacing worn out discs.

Slipping when shifting automatic transmission gears: why does the automatic transmission slip?

Let's start with the fact that the automatic transmission consists of three main parts, each of which performs certain functions.

Torque converter. The torque generated by the engine is increased by the torque converter and then transferred to the planetary gearbox using oil flows and pressure.
The planetary gearbox changes the amount of torque received from the torque converter and the output number of the gearbox in accordance with the driving modes. This happens by blocking some gears and unlocking others. A set of clutches and brake mechanisms responsible for switching between gears block and stop the elements of the planetary gear.
Hydraulic control system. It is designed to control a planetary gearbox.

Normally, an automatic transmission ensures ease of driving a car with automatic transmission and maximum comfort. However, during operation, an automatic transmission, like any other vehicle mechanism, can fail.

As mentioned above, transmission breakdowns often manifest themselves as noticeable jolts when changing gears. The automatic transmission may also slip at different stages. At the same time, the difficulty of diagnosing an automatic transmission malfunction often lies in the necessary complete dismantling of the entire unit.

Signs of automatic transmission slipping

Slipping of the automatic transmission is manifested by slight slipping when the accelerator pedal is sharply pressed or when shifting to a higher gear. With such slippage, traction is lost and the car engine begins to idle.

We also recommend reading the article on how to check the oil in an automatic transmission. From this article you will learn how to check the ATP fluid level in an automatic transmission, as well as how to assess the condition of the transmission fluid and what to pay attention to.

If you continue to operate the automatic transmission without paying attention to this malfunction, then in the future the slipping will increase significantly, the box will begin to slip even when starting from a standstill, as well as when the automatic transmission is switched to both a lower and higher gear.

Why the automatic transmission slips: reasons

Slipping when shifting an automatic transmission to a higher gear often indicates the use of low-quality gear oil or one that has lost its properties. Also in this case, it is recommended to check the oil level. The oil should not be below or above the required mark.

In this case, the problem is solved by replacing the transmission oil and automatic transmission air filter. It should be remembered that replacement can only help with slight slipping when changing automatic transmission gears.

If slipping occurs only when the automatic transmission is switched “to cold,” then it is necessary to check the clutches (friction discs). Friction discs are installed on the planetary gearbox. When the gear is off, the rotation of the friction rings relative to each other is completely free.

When the gears are engaged, the friction rings, pressing against each other, allow the planetary gearbox (sun gears in a certain order) to be rotated. At the same time, clutches are short-lived and wear out over time (with a vehicle mileage of 200-250 thousand kilometers).

The problem of clutch malfunction is solved by replacing them. The work of replacing friction rings is quite labor-intensive and complex, as it requires dismantling and completely disassembling the gearbox, after which the condition of all moving elements inside the automatic transmission is assessed.

Hydroblock. Clogged valve body channels do not allow for a high-quality supply of ATF to the moving elements. The hydraulic unit channels are cleaned using cleaning chemicals under the influence of ultrasound.

This work is carried out only on the removed valve body and is very labor-intensive. Also, after repairing the valve body, it is recommended to replace all filters of the car and, accordingly, the transmission oil in the automatic transmission.

If the oil change is completed, but slipping occurs when the automatic transmission is switched “to hot,” this means that the solenoid block and/or pump has failed. As a result of using low-quality or used oil, solenoids become unusable.

To identify this malfunction, the pressure in the lubrication system is measured. If the pressure in the system is at a low level, then the problem lies in the solenoids or in the pump.

It is solved by replacing all failed elements, and for more correct operation of the automatic gearbox, it is recommended to change the solenoids in “packages”. This will ensure their proper operation and reduce the risk of recurrence of this breakdown.

Another possible reason for the automatic transmission slipping may be a failure in the electronic control unit (automatic transmission ECU). The ECU is a complex electronic device for an automatic transmission. The control system consists of a memory in which automatic transmission control programs are stored.

The unit also interacts with groups of sensors that provide information at each specific moment in time about the state of the controlled area during the operation of the automatic transmission itself, actuators, etc.

To accurately check the automatic transmission ECU and determine the problem, you must contact a service center to carry out high-quality and accurate diagnostics. If a defect is detected, the problem is often solved only by completely replacing the automatic transmission electronic control unit, since the device is often beyond repair.

Automatic transmission does not change gears: reasons

Depending on the brand and manufacturer, automatic transmissions may have some differences, but the main causes of shifting problems are common. Let's start with the fact that the most common mistake leading to automatic transmission failure is turning on the drive mode “D” without stopping when moving in reverse. The same can be said about engaging “R” when driving forward.

You need to understand that “neutral” is a mode that unlocks the wheels for the possibility of short-term towing or moving the car in the event of some kind of malfunction. For an automatic transmission, there is no need to use it during everyday use of the car, as this causes increased wear.

In what cases does the box kick?

There are many reasons why the normal operation of an automatic transmission is disrupted. Let's consider the main ones, as well as possible solutions to problems:

The automatic transmission kicks while driving. This indicates a malfunction of the valve body or torque converter. They will probably need to be replaced.
Shocks are felt in the automatic transmission during braking. A sign of a faulty clutch or valve body. Replacement of failed spare parts will be required.
The box jerks when engaging reverse gear. A broken sensor or possible problems with the torque converter. Replacement required.
The automatic transmission kicks when cold. Transmission components are worn out. Replacement of worn parts.

Let's look at some cases in more detail.

Reasons for delays in shifting gears in automatic transmissions and ways to eliminate them