The  Powertrain and transmission system transmits engine power to the vehicle’s wheels and multiplies engine torque to accelerate the vehicle

Nearly 100 years ago cars had two or three-speed manual transmissions that required an expert hand to operate smoothly. They were noisy, rudimentary systems compared to today’s modern powertrain and transmission systems.

The vehicle’s powertrain and transmission system transmits engine power to the vehicle wheels. It provides for multiplication of engine torque (or twisting force) to accelerate the vehicle from a stop, or for carrying heavy loads in the case of trucks.

The system also allows for engine speed reduction at cruising speeds to save fuel and reduce noise.


Key components of the system include:

Transmission or Trans-axle

Transmission or Trans-axle
Transmission or Trans-axle

First of all, you are making the mistake of calling the gearbox “transmission”.

The car’s transmission are all the components and systems that take the power from the engine to the wheel.

The transaxle is a gearbox like any other, only it’s positioned in the middle of the main drive shaft in a front engine – rear wheel drive car (or a front engine 4×4).

In a front engine / front wheel drive configuration, the gearbox is attached to the engine, incorporating the differential, which then send power through 2 axles to the front wheels.


Transfer Case (four-wheel-drive or all-wheel-drive)

Transfer Case
Transfer Case

A transfer case is a part of the drivetrain of four-wheel-drive, all-wheel-drive, and other multiple powered axle vehicles. The transfer case transfers power from the transmission to the front and rear axles by means of drive shafts. It also synchronizes the difference between the rotation of the front and rear wheels, and may contain one or more sets of low range gears for off-road use.


Propeller Shaft (drives the rear axle)

Propeller Shaft
Propeller Shaft

A drive shaft, driveshaft, driving shaft, propeller shaft (prop shaft), or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drivetrain that cannot be connected directly because of distance or the need to allow for relative movement between them.



Drive Axles (drives the wheels)

New and used Toyoa 4runner drive axle
New and used Toyota 4runner drive axle

An axle that is driven by the engine or prime mover is called a drive axle.

Modern front wheel drive cars typically combine the transmission (i.e. gearbox and differential) and front axle into a single unit called a transaxle. The drive axle is a split axle with a differential and universal joints between the two half axles. Each half axle connects to the wheel by use of a constant velocity (CV) joint which allows the wheel assembly to move freely vertically as well as to pivot when making turns.

In rear wheel drive cars and trucks, the engine turns a driveshaft (also called a propellor shaft or tailshaft) which transmits rotational force to a drive axle at the rear of the vehicle. The drive axle may be a live axle, but modern rear wheel drive automobiles generally use a split axle with a differential. In this case, one half-axle or half-shaft connects the differential with the left rear wheel, a second half-shaft does the same with the right rear wheel; thus the two half-axles and the differential constitute the rear axle.


Clutch (manual shift)

Clutch And Pressure Plate

A clutch is a mechanical device that engages and disengages the power, transmission, especially from driving shaft to driven shaft. Clutches are used whenever the transmission of power or motion must be controlled either in amount or over time.


Torque Converter (Automatic Shift)

Torque Converter

A torque converter is a type of fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine, to a rotating driven load. The torque converter normally takes the place of a mechanical clutch in a vehicle with an automatic transmission, allowing the load to be separated from the power source. It is usually located between the engine’s flexplate and the transmission.

The various components are subject to wear and may malfunction; this can cause abnormal noise, loss of drive or gear ratio, vibration, or other driveability concerns. This may also be accompanied by an illuminated or flashing check engine light or gear range indicator. Ignoring a indicator light can further damage the system or other components.



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