Parts That Make Up a Transmission

by Emilia Lamberto
itstillruns article image
gear image by FXTW from

The first automobiles produced did not offer automatic transmission. Using a clutch, drivers had to manually shift gears to operate the vehicle. As cars grew bigger and more people acquired them, an "automatic" transmission became the focus of future vehicles. Transmissions, whether automatic or manual, are made up of many parts, including several gears. Manual transmissions use needle bearings to help mount the different parts. Both transmissions work differently.

Torque Converter

In an automatic transmission, the torque converter takes the place of the clutch in a manual transmission. A torque converter's purpose is to increase the turning power that the engine provides. This is completed by the rest of the parts in a transmission.

Pump and Turbine

The engine and transmission never physically touch. It works by hydraulic coupling, in which the transmission fluid is caught by blades of a fan, causing them to spin. The impeller, or pump, and the turbine are these blades. Once one fan starts spinning, the other spins. Powered by the centrifugal force, the transmission fluid moves to the outside of the blades and is sent back to the turbine side through the third fan, the stator. Steady transmission fluid flow causes the engine's turning power to multiply.

Planetary Gear Set

In an automatic transmission, there is a planetary gear set. The planetary gear set was designed after the model of our solar system, hence the name. It is made up of different sized gears that are circular in shape and revolve around a "sun gear" which is the central gear. Planetary gear sets differ by type of transmission, but as of 2010, the basic design has not been changed for nearly a century.

Clutch Pack and Transmission Bands

Some vehicles use multiple clutch disc systems, which consist of discs placed between steel plates. The clutch contains one piston and return springs. When the clutch pack is under pressure due to the transmission fluid, the piston locks the assembly together, and when the car is not in gear, the piston disengages. Sometimes a transmission band, a metal ring designed for flexibility, is used instead of the clutch pack. The band sits around the clutch. Engaging the gears requires the band to tighten and loosen to disengage.

Output Shaft

The output shaft connects the transmission to the wheels. The output shaft is attached to the axles in a number of ways, which allows the transmission to turn the shaft and ultimately spin the axles.

Manual Input Shaft

In a manual transmission, the input shaft is mounted in a gearbox at the front. This box is very durable. The front end of the input shaft slides perfectly into the clutch disc. The rear end of the input shaft fits the drive gear at the end of the layshaft.


The layshaft, also known as the cluster gear, is a single unit consisting of the number of gears that the transmission has (three-speed, four-speed, five-speed or six-speed) and often times, a gear for reverse.

Central Shaft

The central shaft runs inside of the layshaft. Needle bearings are used to mount the layshaft. The input shaft creates the power and sends it through the layshaft. From the layshaft, the power is sent to each gear, controlled by the shifter of the vehicle and to the output shaft.

Output Shaft

The output shaft is located at the back end of the gearbox with needle bearings. After the vehicle is shifted, the output shaft then goes into the drive shaft to get the car rolling.


A ring with teeth on the outside of it sits beside the gear. When the driver chooses a gear, the shift hub does the work and the teeth lock itself into the gear. This combination drives the output shaft.

More Articles

article divider