How an Automatic Gearbox Works?

Every driver knows that depending on the incline of the road and the speed you’re travelling at, there’s a range of gears to choose from.

There are two ways of controlling your car’s transmission. It will have either a manual or an automatic gearbox. Most drivers in the UK will be more familiar with a manual gearbox, which uses a gear stick to change between these gears. 

For years, most car gearboxes in the UK have been manual. It’s easy to understand why they’re called manual; you’re choosing and selecting the gears yourself. An automatic gearbox, however, the car is doing it for you.

With the rise in electric cars and hybrid cars, there has been an increase in automatic transmission cars in the UK. With more UK road users adopting these cars, it is important to understand how they work and more importantly, how to look after an automatic gearbox. 

The Differences Between Manual Gearboxes and Automatic Gearboxes

 As there are separate driving tests for both automatic and manual transmission cars, you also get distinct driving experiences. Let’s explore some of the differences in how they drive and what you see in the car.
The first thing you will notice is that it has no clutch pedal on an automatic car. The second thing is that there is no gear stick; a simpler, identical mechanism has been replaced with three standard options: neutral, drive, park and reverse.
Drive – automatically picks gears and makes the car move along.
Park – You can only use it when you are stopped or you get out of your vehicle. It ‘ locks ‘ the transmission stopping it from rolling away (but when stopped, you still need to apply the handbrake).
Reverse – This does as it says acts the same as a reverse gear in a manual, and should be selected when you want to drive backwards.
Neutral – is the same as a manual gearbox knocking out of gear. When driving-this is known as coasting-it should not be used but can be used (along with the handbrake) if you’re stuck for a short time.

Torque Converter

The torque converter’s primary role is to provide connection of your engine’s power to the wheels being driven. Unlike a manual clutch with a connecting flywheel, a torque converter is a fluid coupling that operates by hydraulic pressure. The torque converter has three main components:

  1. The impeller – bolted to a flywheel
  2. The turbine – connected to the gearbox input shaft
  3. The central reactor – connecting these two components

The turning effort is made as the engine speeds up centrifugal forces, which act on hydraulic fluid that sends torque to the turbine.

A Simplified Version

When your car is sat idle after turning it on, the torque converter isn’t creating enough torque to power the turbine, so your car stays stationary.

The torque converter rotates faster when you press the accelerator, which will produce more fluid and torque to the gearset. This causes your car to move.

The torque converter is, nevertheless, a more complex beast. It provides additional torque and power by delivering the hydraulic fluid via its different components and back to the pump. Following that process, your car accelerates to the desired point and releases torque once there to prevent going any faster.

How An Automatic Transmission Gearset Works

An automatic transmission uses three main gearing components, instead of having different sets of cogs to create each different gear ratio for your driving gear:

  1. The sun gear
  2. The planet gears and the planet gears’ carrier
  3. The ring gear

The central player in the automatic gearbox system is the planetary gearset. The central sun gear is connected to the outer ring gear by this system. Multiple gearsets can be working together to achieve the different gear ratios.

Without sounding too technical, the various ratios to expand, reduce or reverse power are generated by locking or connecting these gears to the larger outer ring gear (using clutches and brakes).

Brake Bands and Clutches

You have a large number of brake bands and clutches within your automatic transmission.

Brake bands can be tightened to either keep the ring and sun gear stationary or allow them to spin. These are like a few other components controlled by a hydraulic system.

The clutches connect the planetary gear and release it, activating the necessary gearing required. A combination of mechanical, hydraulic and electrical functions ensures the control of these clutches.

In summary, it’s a complicated but ingenious system that allows your automatic gearbox to work correctly.

How Do I Know if My Automatic Gearbox has Gone?

Your vehicle won’t move if your gearbox has broken. If it is damaged and needs repair, a few tell-tale signs will be provided to help you detect trouble beforehand.

Due to the abundance of hydraulic components in your automatic gearbox, the leaks will normally show as a pool underneath your car.

Another sign that your gearbox may be on its way out will be if it feels clunky as well as making noises when changing gears. You should notice the once smooth transition between gears will have disappeared and instead, you will hear a buzzing, whining or humming sound.

Checking Engine/Gearbox Oil

You check an automatic gearbox’s engine oil the same way you would check your engine oil. Your car will have a dipstick to check your gearbox oil, which is usually at the back of a rear-wheel-drive engine. However, the dipstick will be located on the transaxle near the front of your vehicle if your car is front-wheel drive.

When checking the engine/gearbox oil make sure your car is idling. It’s also a good idea to move the gear selector through each of its positions three to five times and then set it back into park.

If you need to know how to change the oil in your gearbox, there should be a drain plug for small cars and both the sump pan and the dipstick tube for others. Most modern cars won’t even need draining so you won’t find a drain plug.

It can be quite a challenging and messy job, so when you are changing the engine oil it should be handled with care.

The dipstick tube is used to top up low levels. To deliver the transmission fluid you will need a small funnel and you should just add a little at a time until you hit the perfect midway point.

Why Choose Automatic Man?

We are automatic gearbox specialists operating in London and the surrounding areas. We can repair all automatic gearboxes on British, German, American, Japanese and French cars. We can also perform semi-automatic gearbox repairs.

Our qualified technicians can perform all types of automatic gearbox repairs including the reconstruction and replacement of all gearboxes using the high-quality information obtained from our vehicle diagnostics systems. This includes the latest DSG gearbox and many others.

Here at Automatic Man, we offer a free diagnostic session on any automatic vehicle. Automatic Man has a good reputation amongst automatic vehicle owners in London for high-quality service and expertise over the last 34 years.

As a leading gearbox specialist, you can rest assured that your car will receive the highest quality of care. Our automatic gearbox specialists will ensure your car is back on the road and performing well for a seamless driving experience.

If you’re experiencing problems with your automatic gearbox and are looking for a reputable gearbox specialist in London, contact us for free today.

17 thoughts on “How an Automatic Gearbox Works?”

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