Transmission: Definition, Types, And Working

What is a Transmission?

A car transmission is one of the most important components of a vehicle. It’s what moves the power from the engine to the wheels.

There are a variety of car transmissions. Some are automatic, while manual transmissions in shift cars gear require the driver to take additional steps in order for the vehicle to operate effectively.

If you were wondering how a transfer works, the process depends on the type of transmission. Regardless of the type of transmission, the answer to a transmission’s function is to adjust the gear ratio between the drive wheels and the engine as the car slows and speeds up.

When a car is stopped, the transmission separates the engine from the drive wheels so that the engine can idle when the wheels are not moving. Transmissions also allow quick acceleration from a standstill and allow the engine to run slower to reduce wear while the vehicle is traveling at constant speeds.

Transmission Diagram

Automatic Transmission Diagram
Transmission Diagram

1. Manual Transmissions

Manual transmissions have a clutch pedal and a gear lever with which the driver shifts manually. These types of transmissions consist of a set of gears along a pair of shafts called the input and output shafts.

With a manual transmission, the driver has to select the correct gear and engage or disengage the clutch. The transmission uses a flywheel, pressure plate, and clutch to turn the engine on and off from the transmission.

The flywheel and the pressure plate are connected to the engine. The clutch is located between them and is meshed with the transmission input shaft. The term “pushing the clutch” means releasing the pressure plate, which releases the clutch from the motor. Every time you make a shift you have to push the clutch in first.

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Types of Manual Transmission

The following are various types of manual transmissions.

1. Dual-Clutch

This transmission uses two clutches that can be wet or dry. A clutch operates the even gears (2, 4, and 6). The other clutch operates the odd gears (1, 3, 5, and reverse). Dual-clutch transmissions were common in older cars and are still found in modern racing cars.

In today’s automated dual clutch manual transmissions, sometimes referred to as dual clutch transmissions or dual clutch transmissions, a computer controls the engagement and shifting of the clutch, bridging the gap between a manual and an automatic transmission.

2. Unsynchronized

The first manual transmissions were unsynchronized, or “non-synchro.”  They were also called rock crushers because the drivers grind the gears together and try to get them to mesh. Trucks used this type of transmission well into the early 1960s because the transmissions were very powerful.

3. Synchronized/Constant Mesh

Synchronized/constant-mesh transmissions keep the cluster gear, drive gear, and main shaft gears constantly moving. These types of transmission use pads to slow down the gears. This eliminates the need for double-clutching action.

4. Automated 

An automated transmission, sometimes called an AMT, is a manual transmission with a computer that controls shifts and the clutch. The AMT is used in heavy trucks.

5. Single-Clutch

The single-clutch is a manual transmission in which the computer controls the shifting and the clutch. Shift and clutch control can be electrical, hydraulic, or electrohydraulic. The popularity of single-clutch transmissions began to wane when dual clutches were able to handle increased torque.

6. Preselector

A preselector was a manual transmission with a vacuum or hydraulic shift control that was mostly used in the 1930s through the early 1950s. Some preselectors used bands and planetary gears. Basically, whatever forward gear was selected, the next time the clutch was engaged, it shifted to that gear.

2. Automatic Transmissions

The main automatic vs. manual transmission difference is that with an automatic transmission, the process that powers a manual transmission happen within the transmission itself. Automatic transmissions typically don’t use clutches. Instead, the automatic transmission relies on a torque converter to change gears.

The first automatic transmission, which looked more like a semi-automatic transmission because it still had a clutch, has been around in some form since the beginning of the 20th century. The first true automatic transmission to be used in a production car was the Hydro-Matic in a 1939 Oldsmobile for the 1940 model year. The inventor was Earl Avery Thompson.

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Most large SUVs and trucks have conventional automatic transmissions. Here are some terms commonly associated with automatic transmissions.

  • Direct-shift gearbox: A direct-shift gearbox, also called a DSG, has two clutches that disengage alternately in changing gears. DSGs provide smooth acceleration and fast shifting.
  • Tiptronic: A tiptronic gearbox allows an automatic transmission to be shifted manually, via the shifter and/or the steering wheel controls. The drawback is the computer will override/not allow manual mode if the transmission is outside the set parameters.
  • Hydraulic: Hydraulic is the pressure/fluid inside an automatic transmission. What about electric cars? Single-gear systems are used in electric vehicles. The power band of an electric motor enables engineers to use compact single-speed transmissions to transfer power to the drive wheels. This can be integrated with the motor or be a bolt-on.

3. CVT Transmissions

Continuously variable transmissions, Called CVTs, are pulley-based transmissions that are mainly used in small vehicles with small engines. CVTs have been used in snow machines, ATVs, and side by side for years, to name a few. They have also recently become popular in hybrid vehicles.

The default setting is a primary small drive and a secondary large powered clutch with a belt or chain to connect the two. The belt or chain sits deep in the primary drive and high in the secondary drive at a stop.

When you accelerate, the primary drive contracts causing the belt or chain to move up, while at the same time the secondary drive expands and the belt or chain moves down.