Automatic transmission jerks when you hold the brake

Many drivers have had to deal in practice with such an incomprehensible and unpleasant situation when the automatic transmission of a car suddenly begins to act up, to function not as usual, but with obvious deviations from the norm. When it is switched, shocks appear; often, for no apparent reason, the automatic transmission “kicks” when braking or starting to move from a standstill.

Eliminating problems with automatic transmission when braking.

Automatic transmission: jerking when braking

As you know, during the operation of an automatic transmission, it is important to pay attention to the slightest changes in the operation of the unit. Often, the first sign of various problems is the appearance of jerks and jerks in the automatic transmission when shifting gears “up” (during acceleration).

However, a situation where the automatic transmission kicks when braking is also an alarming symptom. In this case, this may also indicate problems with the unit, which will only progress in the future.

Next, we will look at why automatic transmission jolts occur when braking, when accelerating, or at a standstill when switching between different automatic transmission modes.

When the box has nothing to do with it

It should be noted that the reason why a car suddenly starts to twitch strangely when starting to move, braking or accelerating for no reason at all is not always the automatic transmission. There are cases when this occurs due to the influence of low-quality fuel or interruptions in the ignition system. Since the car is one system unit, a malfunction in the operation of the engine or ignition automatically leads to deviations in the functioning of the automatic transmission. Then car diagnostics are also inevitable.

The driver should make it an ironclad rule to follow technical recommendations and preventive measures that will make it impossible or, in the extreme case, delay as long as possible a malfunction in the operation of the vehicle. This is, first of all, filling the engine with only the high-quality oil recommended by the manufacturer. In addition, strict adherence to the interval for replacing filters and fluid and, as already noted, warming up the automatic transmission when using the car at low temperatures are mandatory. Of course, you also need to operate your car carefully and from time to time have it undergo a full technical inspection, using the services of reputable service centers and good diagnosticians.

Automatic transmission jolts: when braking, while driving or standing still

So, the appearance of jerks, jerks and kicks of automatic transmissions is the main problem of all automatic transmissions without exception. Taking into account the fact that an automatic transmission is an expensive and complex unit, such failures are a serious reason for diagnosing the automatic transmission.

In this case, the automatic transmission kicks for a number of reasons; the shocks and jerks themselves can be constantly present, or the problem can be “floating”, appearing only in cold or hot weather, under high or low load conditions, etc. If we talk about kicks during braking, first of all, you need to be able to distinguish a breakdown from the operating features of the unit. Considering that the hydromechanical automatic transmission remains the most common, let's focus our attention on such an automatic transmission.

This results in the gear shift moment becoming more pronounced. In some cases, this even leads to the appearance of small shocks, both during acceleration (gears shift up in steps) and during braking (shifts down in steps).

If you start to brake sharply, the box needs to quickly switch, for example, from 4th gear to 1st. Naturally, the gearbox may simply not “keep up” with cold oil, which causes the automatic transmission to jerk when braking, which is especially noticeable almost at the moment the car comes to a complete stop. Moreover, after the automatic transmission warms up (after 10-15 km), all shifts return to normal, as the oil heats up and fully reaches operating temperatures.

In the case when the shocks remain even on a warm automatic transmission, in this case the box needs diagnostics. To understand why the automatic transmission kicks, you need to start by checking the oil in the automatic transmission. The oil (ATF transmission fluid) should be clean, transparent, without a burning smell, the “hot” level on the dipstick should be between o and “hot”.

If there are any comments regarding the oil level or oil level, it is necessary to change the oil in the automatic transmission, at the same time replacing the automatic transmission oil filter. If the level deviates from the norm, you will need to add oil to the box or remove excess ATP from the unit, since overfilling the automatic transmission with oil can also lead to malfunctions of the machine and often causes increased wear.

After making sure that the cause is not oil, you need to move on to malfunctions of the valve body or torque converter. As a rule, problems with the valve body often arise as a result of solenoids failing. Solenoids usually last about 100-150 thousand km. The valve body itself may also be damaged. In this case, the valve body is repaired or completely replaced.

Please note that it is for this reason that it is recommended to change the automatic transmission oil every 40-50 thousand km, as well as perform preventive maintenance of the gas turbine engine every 100-150 thousand km. mileage At the same time, it is necessary to change the automatic transmission filters, as well as flush the unit or individual systems before changing the oil.

Let us also add that if the automatic transmission kicks when shifting, when engaging D or R, as well as when braking, this often indicates the need to repair the gearbox itself. More precisely, the malfunction may be caused by problems with the clutches.

To troubleshoot problems, you will need to dismantle the automatic transmission, after which the unit will be completely disassembled. Then specialists carry out troubleshooting, change clutches and a number of other elements.

In cases where the automatic transmission kicks when the reverse gear R is engaged, and the automatic transmission jerks during braking or when moving forward, in addition to problems with hydraulics and mechanics, various sensors and electronic components may arise.

To accurately determine the malfunction, you should perform computer diagnostics of the automatic transmission. It was noted that the automatic transmission often kicks when braking precisely because the firmware of the control units is simply outdated. This feature is quite common on different cars and can be solved by installing a more recent version of the software (firmware update).

The main thing is that automatic transmission flashing must be performed in centers that separately specialize in the repair and maintenance of automatic transmissions. It is highly not recommended to carry out such operations using makeshift methods in a garage, since the unit may begin to work incorrectly, the electronic units may malfunction, or the box itself may quickly fail.

What to do if the reason is ATF

Often the reason why a car experiences a shock or a jolt during braking is that the ATF level does not correspond to that recommended for normal operation of the unit. It turns out that if the working fluid has an excess or deficiency, this can provoke foaming. Then the automatic transmission pump fails to pump a sufficient volume of oil to the parts in contact one with the other. Constant oil deficiency leads to wear of some parts. Their forced contact “dry” ends in an unwanted jerk of the car, leading to strange jolts, and even sharp impacts when one of the gears is engaged. This is doubly undesirable for a car when it operates for a significant period of time in urban conditions, where there are constant changes in speed due to traffic jams, irregular traffic on roads with traffic lights, etc. In such conditions, problems with the automatic transmission progress literally before our eyes.

The following logical algorithm suggests itself: having detected the automatic transmission twitching when switching, the first step should be to check the fluid level. It should definitely be brought back to normal by adding the required amount or, if there is excess, draining the excess. Then check the fluid for cleanliness. If signs of contamination are found, replace it. It will also be necessary to change the filter, remove deposits from the filter mesh, etc. We must not forget that the box certainly requires that it be warmed up at a low temperature before starting to move.

Let's sum it up

As you can see, the problem with shocks, jerks and inclines of the automatic transmission is quite common. In some cases, it will be enough to replace the automatic transmission oil and filters or reflash the automatic transmission ECU (install the latest software version), while in others it is necessary to carry out in-depth diagnostics, remove the unit from the car, disassemble and replace worn/broken elements.

For this reason, it is recommended to maintain this unit in a timely manner, follow all the operating rules of the automatic transmission, avoid high loads unless absolutely necessary, and also use high-quality transmission fluids and consumables, which must be changed strictly according to the regulations or even earlier (taking into account the individual characteristics and operating conditions of a particular vehicle ).

Overheat

A properly functioning cooling system is an important component of the health of the machine. Jerking of the box can be caused by simple overheating of the working fluid. This happens, for example, when pushing for a long time in traffic jams in the heat, when, in addition, the cooling radiators are clogged or the thermostat of the transmission cooling system is stuck in the closed position. The first case often occurs, for example, on the penultimate generation Ford Mondeo with a 6-speed Aisin automatic transmission, and the second on BMW models with a ZF 6HP unit.

Control block

A faulty transmission control unit is another possible culprit for shock switching of the machine. Structurally, it can be either an independent unit or a built-in unit of the “brains” of the engine. For example, on the second generation Mazda 6, a separate automatic transmission unit is installed in the vehicle interior. For diagnostics, you can substitute a known-good module from another machine of a similar modification. The replacement procedure does not require block programming, has no pitfalls and immediately eliminates a lot of questions.

Mechanical part

Gear shifting in a hydromechanical automatic is carried out by blocking certain elements of the planetary gears. Clutch packs or band brakes are responsible for this. Due to a large number of faults, they can operate with slipping, causing jerks when switching.

For example, on Audi models with a 6-speed ZF automatic transmission, increased wear of the drum bushings is encountered. Through them, oil is supplied under pressure to the clutch pack. Fluid leaks through enlarged gaps eventually lead to disc slipping and burning.

If you experience problems with the operation of the machine, it is very important not to put off a visit to the service center for a full diagnosis. After all, the nature and cost of repairs will depend on this. In case of internal mechanical problems, the unit will have to be removed and completely disassembled, but the electrical part can often be cured by simply dismantling the pan and the hydraulic unit of the box.

Why does the machine twitch?

An emergency situation, when the car’s automatic transmission “kicked” and twitched unpleasantly, is familiar to many. In such cases, some drivers, without delving into the reasons for what was happening, turned for help to service centers or to familiar professional automotive mechanics, who began to troubleshoot problems, often completely rebuilding the box, thoroughly changing one of the main blocks or even several of them . This method of adjusting an automatic transmission, of course, also has a right to life, however, it would be much more logical if the driver himself thoroughly understood the reasons for what happened in order to understand in the future what is happening.

Often it’s not that difficult to figure out. In modern cars with an automatic transmission, kicking is often caused by turning on the “Drive” mode. This problem can often be resolved by simply changing the oil in the transmission, after which the unwanted shocks will completely disappear. However, this does not always happen; sometimes even after a complete change of oil and filter element, no positive changes will occur, the shocks remain. Then the car owner will have to resort to full diagnostics in order to accurately find out the real cause and then eliminate it.

OFF. The car jerks when the brake is pressed on D

The car began to shake when accelerating, at the very beginning of movement, and then when stopping, the body twitches when the brake is pressed in D. The engine check does not light up, but the car is running unstable. It is not noticeable when moving.

This happened six months ago, after resting the car overnight everything was ok.

I changed the spark plugs and cleaned the throttle body. where else to watch? The glitch is not permanent.

Yeah, a real hystrotransformer. 6 steps. and what kind of budulik? Can you be more specific?

It’s strange that there is silence on the on-board computer!

I have the same glitch since the new one with GenBorom 2.5+automatic transmission 6st. It’s not a fact that a donut can have all sorts of ESP and HLA that block rollback, etc.

True, this only happens on an unheated transmission. when the wheel's anti-recoil system locks.

Ford "cancel", yeah. for diagnostics of the gearbox and torque converter for starters..

+ on subariks it was that the XX regulator was clogged with dirt

and on your engine I don’t even know if it’s even there, this IAC. also, the mass air flow sensor can be a fool, but again, I don’t know if your car has it

I once had what you describe. Exactly. The Nissan Maxima has an automatic transmission (but the old lady is ’99, at that time she was 7 years old). And then they also told me that I would blow on the diagnosis of the machine. However, the problem turned out to be the coils. There is a coil on each candle (6 in total). Using the method of sequentially throwing off the wires, I discovered the faulty one and changed it myself (lucky - it was in the “nearby” head). Everything is over.

The car is, of course, a friend, but the symptoms are too similar to mine!

Source

When you turn on the automatic transmission, the car jerks: the main reasons

The automatic transmission is a fairly reliable unit, but during operation the possibility of various malfunctions should not be ruled out. As a rule, the main sign of problems are shocks, jerks and kicks of the automatic transmission, which can occur both when switching gearbox modes on the spot and while moving.

Let us note that quite often the driver notices the appearance of automatic transmission jolts when the car is stationary, when when turning on “D” the car jerks, jolts appear when turning on the “R” mode (reverse), etc. In this article, we will look at why the car jerks in an automatic transmission when you engage reverse gear, and also what jerks indicate when shifting into “D” (drive).

What does it mean when the automatic transmission kicks?

So, car owners are often faced with the fact that various malfunctions of an automatic transmission significantly reduce driving comfort or make further operation of a vehicle with this type of transmission completely impossible.

As a rule, most often a car with an automatic transmission begins to twitch; when changing gears, jerks, jolts, and impacts occur. Less often, gears can be “dragged”, there is a delay in switching, and so-called slipping occurs.

Let us immediately note that in practice, automatic transmission kicks look like this:

Also, the automatic transmission can only push when it’s cold, the automatic transmission kicks when it’s hot or occurs constantly. You can also note that the box can only push in certain gears (for example, when moving from 1st to 2nd, from 3rd to 4th, etc.).

One way or another, such operation of the gearbox indicates problems and the need for automatic transmission diagnostics. In this case, based on one or another indirect signs indicated above, you can try to more accurately determine the nature of the malfunction.

Automatic transmission: why does the car jerk when you turn on the speed?

So, as mentioned above, if the automatic transmission kicks, pushes or jerks when changing gears, in some cases this indicates possible malfunctions and deviations from the norm. Taking into account the fact that today there are several types of automatic transmissions, with the most common type being a hydromechanical gearbox, we will focus on this type of automatic transmission.

First of all, it is important to understand that slight jolts from the automatic transmission can be considered normal under certain conditions. Please note that a hydromechanical automatic transmission differs from a variator in that it is stepped, that is, the moment of gear shifting is more or less noticeable to the driver, especially in lower gears (for example, moving from 1 to 2). In other words, there will be no absolutely imperceptible and smooth switching.

The oil in the automatic transmission transmits torque from the engine to the box in the torque converter (automatic transmission donut), and also circulates under pressure through the channels of the valve body, influencing the actuators. In fact, the liquid is a working fluid that is actively involved in the processes of controlling the entire operation of such a gearbox.

It is not difficult to guess that a change in the properties of the transmission oil in an automatic machine can cause jolts and kicks. For example, as the outside temperature decreases, the ATF viscosity also changes. This means that “in cold weather” when you turn on D or R, a slight push from the machine may be felt. The reason is that the oil is cold, more viscous, fluidity is reduced, and it is more difficult to pump it through valves (solenoids) and channels.

If the problem does not disappear after warming up or the shocks appear in the warm season, then you must first check the condition of the transmission fluid (color, smell), as well as the oil level in the automatic transmission. As a rule, if the transmission begins to kick or jostle when changing gears while standing still or while moving, this in many cases indicates problems with the oil.

The oil in the automatic transmission transmits torque inside the torque converter, while heating up to high temperatures. ATF also heats up automatic transmission wear products, chips, dirt, deposits, etc. One way or another, the viscosity changes (the liquid either thickens or thins). In any case, shocks and jerks when shifting automatic transmission gears are inevitable in this case.

It is enough to remove the automatic transmission dipstick and assess the condition of the oil. If it is dark, opaque, inclusions and particles are visible, then you need to immediately carry out a complete oil change in the automatic transmission (including cleaning the pan), and also be sure to change the oil filter.

At the same time, the automatic transmission oil filter is also changed, since the filter element traps dirt and chips, that is, it becomes clogged over time. The result is that the oil does not flow in full, pressure losses occur, which leads to incorrect operation of various mechanisms and elements (for example, friction discs).

As for the oil level in the automatic transmission, this level is checked only “hot”, that is, after the ATF in the transmission has completely warmed up. Normally, the level should be in the middle, between the HOT and COLD marks. It is important to understand that both a decrease in the level and its excess are not allowed.

Automatic transmission diagnostic methods

Many years of practice have made it possible to develop a clear and effective method for diagnosing a car’s automatic transmission in case of any malfunctions, even when the automatic transmission is pushed. This technique is identical for cars of any brand that has it, regardless of the manufacturer, and involves a set of verification actions. These include a thorough check:

signs of deviation from the norm;
quality and level of liquid;
engine operation in low, medium, high speed modes;
pressure in its hydraulic system.

The car jerks when changing gears while driving: automatic transmission jolts

So, above we looked at the main problems that can cause automatic transmission jolts when switching different automatic transmission modes on a stationary car. Often these same reasons can lead to the car jerking while moving. However, if the automatic transmission jerks while driving, attention should be paid to other possible problems.

Let's start with the fact that if, when checking the transmission oil, it was revealed that the lubricant has a burnt smell, this may indicate problems with the automatic transmission clutches. In a nutshell, friction discs act as a “brake” for the gears inside the automatic transmission. The clutch packs compress and unclench, thereby slowing or stopping one gear and forcing others to work.

Further, this problem progresses, the gears may not engage completely, and when switching from mode to mode, the box does not work correctly. In this case, the machine needs to be disassembled, defective, clutches and other parts changed if necessary.

The next reason for the appearance of jerks and jerks in the automatic transmission is considered to be overheating of the automatic transmission. You need to know that the oil in the gas turbine engine gets very hot during operation. If the critical temperature threshold is exceeded, the properties of the oil may change. Severe overheating leads to the fluid coagulating, disrupting the operation of the entire automatic transmission, and increasing wear on the unit.

To prevent this from happening, manufacturers often install an automatic transmission oil cooler. The task is to remove excess temperature and cool the lubricant. However, some automatic machines (especially old ones) may not have an automatic transmission oil cooler. Also, versions with a radiator can still overheat due to the fact that the radiator is clogged with dirt from the outside, the oil circulation in it is disrupted from the inside, etc.

To solve the problem, along with changing the oil, you need to remove the radiator, wash it, and clean the outside. Only in this case can we talk about the normal operation of the entire system. If there is no radiator initially, and the oil in the automatic transmission overheats, many car owners independently install an automatic transmission oil cooling supplementary radiator.

Another common reason why automatic transmission jerks and a car with an automatic transmission jerks is the automatic transmission oil pump (oil pump), valve body and solenoids. The oil pump creates oil pressure in the machine. Although cases of its failure are not so common, problems with the oil pump also lead to the fact that there is no required pressure, shocks and jerks appear.

In other words, oil is supplied through a channel under pressure and acts on the clutches, which compress and decompress. It is not difficult to guess that if the channels in the valve body are dirty or damaged, the pressure in the system drops, the clutches begin to slip, and the automatic transmission jolts when shifting.

Also installed in the valve body are solenoids - valves necessary to open and close the channels in the valve body at the command of the automatic transmission ECU. These valves allow you to supply fluid to the actuators through channels, as well as stop the supply, regulate the oil pressure in the automatic transmission, etc. It is quite obvious that solenoids can also fail.

They may either not block the channel or not open it in a timely or complete manner. In any case, the box jerks when shifting, gears may not engage, etc. Moreover, on modern automatic transmissions, solenoids may have a plastic housing, which simply melts when the machine overheats severely. If there are problems with the solenoids, you will need to remove the valve body to check and replace these elements.

The list of problems is completed by possible problems with electronics. As a rule, the wiring coming from the ECU to the solenoids may fail. Wires often oxidize, break, contact is broken, etc. Naturally, if there is no signal from the ECU to the solenoid, the automatic transmission begins to kick.

Less often, the automatic transmission ECU itself may fail. Shocks may also occur as a result of faulty ECM sensors. In simple words, the operation of the automatic transmission can also be affected by a faulty TPS, etc.

Troubleshooting Methods

Now let's move on directly to the description of repair work that can be used to fix the problem when the car brakes jerkily at low and/or high speeds. We list the methods in the same order as the reasons. So:

Airing the system . In this case, it is necessary to pump it, remove the air and add the required amount of new brake fluid. You will find the relevant information in the material, which describes how to properly bleed the brake system of a car.
Warped brake disc . There are two possible options here. The first is that if the thickness of the disk is large enough, then you can try to grind it on a special machine. To do this, seek help from a service station or car service center. However, not all services perform such work. You can contact a familiar turner. The second option is more rational and safe. It consists of completely replacing the disk if its deformation is significant and/or the disk is already worn out and quite thin. In this case, it is better not to take risks and make an appropriate replacement. And you need to change discs (drums) in pairs (left and right at the same time). Checking the disk yourself only makes sense if the disk is severely damaged. Therefore, it is better to carry out inspections, and even more so repairs, at a specialized service station.
Incorrect installation of disks . To correct the situation, you must remove and install the disk/disks exactly in accordance with the instructions.
Drum curvature . There are two ways out here. The first is to give it to a turner for boring. The second is their replacement. Depends on the degree of wear and curved geometry of the drums. But it is better to install new nodes.
Worn pads . In this case, everything is very simple - you need to replace them with new ones. The main thing is to choose them correctly. And the replacement procedure can be performed independently (if you have experience and understanding of such work) or in a car service center.
Pad sticking . It is necessary to carry out repair work on the lift to restore the functionality of the pads and calipers. It is best to replace the used pads with new, good quality ones to prevent similar situations from occurring in the future.
The calipers are loose . Repair in this case is impossible. It is necessary to replace the calipers, pins, and, if necessary, pads. When reassembling all components, do not forget to lubricate everything thoroughly with caliper and guide grease.
Inconsistency between the softness of discs and pads . When choosing these and other nodes, you need to pay attention to the corresponding stiffness value. If necessary, replace some or other parts.
Large play in wheel bearings . Here, most likely, you will have to replace the corresponding components. You can try to repair them, however, as practice shows, such an idea is ineffective.
Rust on the brake disc . If the rust deposit is small, then you can do nothing, but operate the car for 500.1000 kilometers until the rust is naturally removed under the influence of the brake pads. Another option is to groove the discs. In fact, the second option is preferable, but more expensive.
Damaged silent blocks . It is necessary to inspect the mentioned components and, if necessary, replace them.