Used VW Gearboxes For Sale

In layman’s terms, your drivetrain is a system that converts engine power into a controlled power source. It acts as an intermediary between the engine and the wheels and converts the power generated by the engine into torque (rotating force), which is then transmitted to the axles, which in turn rotate the wheels. Therefore, without the transmission, your car would literally become useless junk.

The car’s engine generates power and transfers it to the crankshaft, but the power generated is too high and too variable to provide a usable speed for the driver. The engine runs at a rotational speed (600 to 7000 rpm) and the wheels rotate at a slower speed (0 to 1800 rpm). The transmission is able to maintain both your engine speed and wheel speed at optimal speeds and transfers power to the differentials that rotate the wheels. This is due to the gear ratios, but how do they work?

The transmission uses gears that interact with each other to create torque. Let’s say you have a 20-tooth input gear that interacts with a 10-tooth output gear. To turn a 20-tooth gear once, the 10-tooth gear must make two complete turns. The gear ratio is calculated by taking the number of teeth in the output gear and dividing it by the input gear. So the gear ratio in this example is 1: 2, but it is usually simplified to 0.5: 1 to indicate how many times the output gear must rotate for the input gear to make only one full revolution.

How does the gearbox work?

There are many different gear sizes in the gearbox, allowing for different gear ratio combinations. The gear ratios have to be changed depending on the speed of the car, and therefore there are several gears that can be shifted, and the combination of these gears allows the car to travel at different speeds.

As an example, the gear ratios for a Chevrolet Corvette C5 Z06 manual transmission are listed:

• 1st gear: 2.97: 1
• 2nd gear: 2.07: 1
• 3rd gear: 1.43: 1
• 4th gear: 1.00: 1
• 5th gear: 0.84: 1
• 6th gear: 0.56: 1
• Reverse: 3.38: 1

How does an automatic transmission work?

Automatic transmissions came after manual transmissions, and if you understand how a manual transmission works, you already have a basic understanding of how an automatic transmission works. While the manual transmission requires the driver to manually change the gear ratios, the automatic system does this on its own using fluid pressure. Automatic transmission fluid provides the necessary pressure to activate the clutches and bands, which in turn determines which gear the car should be in.

Transmission fluid flows into the torque converter, which activates the clutches and bands. In turn, it determines which gear ratio should be engaged, and then the planetary gear can be set to the correct combination.

What does the transmission consist of?

Transmission housing

The gearbox housing contains all the gearbox parts. It looks like a bell, which is why it is often called a “bell”. The gearbox housing is usually made of aluminum. In addition to protecting all moving gears, the bell on modern cars has different sensors that monitor the input rpm from the engine and the output rpm for the rest of the car.

Torque converter

Have you ever wondered why you turn on the engine, but the car remains in place? This is because the flow of power from the engine to the transmission is cut off. This shutdown allows the engine to continue running even if the rest of the vehicle’s transmission is not receiving any power. On a manual transmission, you disconnect power to the engine from the transmission by depressing the clutch.

But how do you disconnect the engine power from the transmission on an automatic transmission without a clutch?

For this, a torque converter is used.

This is where the black magic of automatic transmissions begins (we haven’t even gotten to planetary gears yet). The torque converter is located between the engine and the transmission. It is a donut-like element that sits inside a large hole in the transmission bell. It has two main functions in terms of torque transmission:

1. Transfers power from the engine to the transmission input shaft.
2. Multiplies the motor output torque.

It fulfills these two functions thanks to the hydraulic power provided by the transmission fluid inside the transmission.

To understand how this works, we need to know how the different parts of the torque converter work.

Elements of the torque converter

Most modern cars have four torque converter parts:

1. Pump,
2. Turbine,
3. Stator,
4. Torque converter clutch.

Pump (aka impeller). The pump looks like a fan. It has a bundle of blades emanating from its center. The pump is attached directly to the converter housing, which in turn is bolted directly to the engine flywheel. Therefore, the pump rotates at the same speed as the engine crankshaft. The pump “pumps” the transmission fluid outward from the center towards.

Turbine. It is located inside the transmitter housing. The turbine is connected directly to the transmission input shaft. It is not connected to the pump, so it can move at a different speed than the pump. This is very important as it allows the engine to run at a different speed than the rest of the transmission.

The turbine rotates thanks to the transmission fluid that comes from the pump. The turbine blades are designed so that the resulting fluid moves to the center of the turbine and back to the pump.

Stator. It is located between the pump and the turbine. It looks like a fan blade or an airplane propeller.

The stator does two things:

1. more efficiently sends the transmission fluid from the turbine back to the pump, and
2. increases the torque from the engine to help propel the car, but then sends less torque if the car is moving at high speed.

This is achieved thanks to modern engineering. First, the blades on the reactor are designed in such a way that when the transmission fluid exiting the turbine hits the stator blades, the fluid is discharged in the same direction as the rotation of the pump.

Second, the stator is connected to the stationary shaft on the gearbox via a one-way clutch. This means that the stator can only move in one direction. This ensures that the fluid from the turbine is directed in one direction. The stator starts rotating only when the speed of the fluid from the turbine reaches a certain level.

(These two stator components make the pump easier to operate and generate more fluid pressure. This in turn creates more torque on the turbine, and since the turbine is coupled to the transmission, more torque can be sent to the transmission and the rest of the vehicle.)

Torque converter clutch. Thanks to hydrodynamics, some of the engine’s power is lost as the transmission fluid flows from the pump to the turbine. This leads to the fact that the turbine rotates at a slightly lower speed than the pump. This is not a problem if the car is just starting to move (in fact, the difference in speed allows the turbine to transmit more torque to the transmission), but once it reaches a significant speed, this difference leads to inefficiency in energy use.

To minimize energy waste, most modern torque converters have a torque converter clutch connected to the turbine. When the car reaches a certain speed (usually 45-50 km / h), the torque converter clutch engages and causes the turbine to rotate at the same speed as the pump. The computer controls the engagement of the converter clutch.

How does a torque converter work?

• You start the car and at the beginning it idles. The pump operates at the same speed as the engine, transferring transmission fluid towards the turbine, but since the engine does not spin very quickly at dead center, the turbine also does not spin at high speed, so it cannot supply torque to the transmission.
• You step on the gas. This makes the engine turn faster, which makes the converter pump run faster. As the pump starts to accelerate, the transmission fluid moves out of the pump quickly enough to start the turbine at accelerated speed. The turbine blades direct fluid to the stator. The stator is not yet rotating because the transmission fluid speed is not high enough. But due to the design of the stator blades, when liquid passes through them, it draws the liquid back into the pump in the same direction that the pump rotates.

This allows the pump to move fluid back into the turbine at a higher speed and builds up more pressure. When the fluid returns to the turbine, it does so with more torque, resulting in the turbine transferring more torque to the transmission. The car starts to move forward.

• This cycle continues over and over as the vehicle accelerates . As you accelerate to high speed, the transmission fluid reaches a pressure that makes the reactor blades finally spin. As the reactor rotates, the torque decreases.

Important: At this stage, you do not need a lot of torque to keep the car going because it is already moving at a sufficient speed. Next, the torque converter clutch engages and makes the turbine rotate at the same speed as the pump with the engine.

Planetary gears

When your car reaches a higher speed, it needs less torque to keep it going. In this case, the transmission can increase or decrease the level of torque transmitted to the wheels, due to the gear ratios (the lower the gear ratio, the more torque. The higher the gear ratio, the less torque).

What are the components of the planetary gear?

1. Sun gear. Located in the center of the planetary gear.
2. Planetary gears and their carrier. Three or four smaller cogwheels that surround the sun cogwheel and are in constant meshing with the sun cogwheel. Planetary gears (or gears) are mounted and supported by a carrier. Each of the planetary gears rotates on their own separate shafts that are connected to the carrier. Ring transmission.
3. The ring gear is external and has internal teeth. An annular gear surrounds the rest of the gear and its teeth are in a permanent mesh with planetary gears.

Note: One planetary gearbox can provide reverse drive and five levels of forward travel. It all depends on which of the three components of the gear train is moving or held stationary.