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Automatic transmissions - how to avoid malfunctions and improve efficiency

Automatic transmissions - how to avoid malfunctions and improve efficiency
Automatic transmission is an automatic transmission that independently determines and switches the gear ratio, adapting to the speed selected by the driver. This ensures a smooth start and smooth ride of the vehicle.

From a technical point of view, both a CVT and a robotic gearbox can be called an “automatic”, since these transmissions change gears automatically, without driver intervention. But the name automatic transmission is assigned only to units equipped with a hydromechanical planetary gear.

Design and operating principle of automatic transmission

At this stage of development of the automotive industry, automatic transmissions are superior to their mechanical counterparts in many respects. Largely due to speed and comfort: automatic transmission relieves the driver of a greater burden when driving, compared to manual transmission. The main advantage of an automatic transmission is that these transmissions save attention, due to which the driver focuses as much as possible on the road. Although experienced motorists shift gears on a manual transmission on an instinctive level, even such “unconscious” actions take away their strength.

Автоматические трансмиссии — как избежать неисправностей и повысить эффективностьAutomatic transmission shift lever. Photo: YouTube.com

Let's analyze the automatic transmission device. This will help you understand the operating principle of the unit. In the classic version, the main elements of an automatic transmission are as follows:

✅ Hydrotransformer. Designed to transmit force from the internal combustion engine to the drive wheels. Structurally, it is a metal body filled with ATF oil
✅ Oil pump. A pump is needed to pump oil
✅ Hydroblock. A hydraulic valve plate consisting of sensors, solenoids, valves and channels connecting them. Designed to regulate speed limits
✅ Planetary gearbox. Shifts gears in accordance with changes in gear ratios
✅ Front and rear clutch, brake band. These elements provide gear shifting

Structurally, the torque converter includes a centrifugal pump, a stator, a pump and turbine wheel, and a centripetal turbine. The stator device is a guide unit. The pump wheel is connected to the engine crankshaft, the turbine wheel is connected to the gearbox shaft. The torque converter is necessary to dampen serious shocks transmitted by the transmission to the engine and back.

The operating principle of an automatic transmission will differ depending on the type of automatic transmission. In classic automatic transmissions, it consists of changing the torque from the ATF pressure pumped by the oil pump into the torque converter. Oil circulating through the reactor impellers transforms mechanical force into hydraulic force. A torque converter is a unit that performs the tasks of both a hydraulic coupling and a clutch.

Automatic transmission in a removed unit. Photo: YouTube.com

The design of the automatic transmission consists of a number of controllers and electronic elements that transmit data on the operation of the box to the ECU. The transmission may include several pressure sensors that determine the intensity of oil circulation, ATF (lubricating fluid) temperature, selector position, shaft rotation speed, gas pedal position, brake pedal, etc.

Malfunctions specific to automatic transmissions

An automatic transmission is a unit that requires proper maintenance. Untimely maintenance is usually the main cause of automatic transmission problems. Moreover, in practice, one problem in a machine quickly turns into another. For example, wear on brake bands and clutch discs can lead to oil contamination, which subsequently clogs valves and oil passages.

Some problems can be identified without dismantling and disassembling the box:

✅ The car moves in parking mode. The reason is wear and malfunction of individual parts of the gear shift mechanism or a violation of the adjustments of this mechanism
✅ Oil leak from box. The problem may be a violation of the integrity of the seals and arbitrary unscrewing of the fastening components in the pan or clutch housing. It is necessary to change the sealing elements and tighten the bolts
✅ The automatic transmission began to work very loudly. It is possible that the gears are changing spontaneously. Most likely, the oil level has dropped below normal
✅ The gear does not downshift when you release the gas pedal. The reason should be sought in a malfunction of the throttle valve drive or incorrect adjustment. Damaged parts will need to be replaced
✅ The car does not move in one of the selected gears. A complete diagnosis of the unit is required: from the level and quality of the oil, to the torque converter, valve body solenoids and oil pump gears
✅ The car only drives in reverse gear or forward. In the first case, diagnostics of valve body valves, clutches, forward clutch and piston is necessary. In the second, the friction elements and the brake band piston are also checked.

One of the problems with the automatic transmission is slipping of the clutches when going uphill or changing gears. First you need to check the discs and direct clutch for wear and the transmission fluid level. If everything is in order, the filter, piston, and hydraulic unit solenoids are diagnosed. Diagnostics of valve body valves and friction clutch discs is necessary in case of shocks when changing gears.

Connection diagram between engine and automatic transmission. Photo: YouTube.com

In an old-style automatic transmission, a typical malfunction is the failure of the lever linkage. Because of this, the box is not able to switch modes. To restore its functionality, it will be necessary to replace the failed selector and rocker.

Operating Tips

The operating life of the unit depends on the conditions of use. Correct and timely maintenance will increase the service life of the box.

Several recommendations for operating cars with automatic transmission:

✅ Changing gears on the go is prohibited. But often this will not be possible, since most cars have a lock
✅ The engine is started in Parking (P) mode, not Neutral (N). To stop safely, always squeeze the brake, then pull the handbrake, turn on mode P and turn off the engine.
✅ Long-term towing of cars with automatic transmission is not recommended. If you need to tow the car, start the engine and turn on N mode
✅ It is prohibited to coast when the neutral mode is on. It is not recommended to tow trailers exceeding the maximum possible load.
✅ It is prohibited to squeeze the brake and gas at the same time. This will cause the engine to stop, but the main impact will be on the torque converter or clutch (on robots)
✅ You cannot turn on D mode when reversing until the car has completely stopped

Proper operation of a car with an automatic transmission is the key to the longevity of the unit. It is not always possible to find competent specialists who can diagnose automatic transmissions and know how to repair automatic transmissions. This circumstance raises the price tag for transmission repairs.

Automatic transmission removed. Photo: YouTube.com

Automatic transmission is more convenient and easier to operate than manual transmission. If you've driven a manual for a long time, adapting to an automatic may take some time. But automatic transmission is the future, and the comfort you will receive outweighs all its potential disadvantages.


Photos used: youtube.com

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