General Terminology

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Table of Contents

Left Vs Right Side of Car

Often when you are buying a part at the auto parts store you are asked if the part you need is for the driver’s side or passenger’s side of the car. In the professional world, the sides of the car are called left and right. The only reason the automotive parts stores, that cater to the public, changed it to the driver’s side and the passenger’s side is to reduce confusion which could lead to the wrong part being sold.

If you ask someone outside the automotive service industry if they are referring to the left or right side of a car, they will usually ask if that is referenced to sitting in the car or looking at the car from the front. The answer. It is while sitting in the car looking out the front window as shown in the image below.

Image 1: The left/right side of a car is referenced to sitting in the car and looking forward

Longitudinal Vs Transverse

Longitudinal Direction

Longitudinal is used to reference a force or direction that runs through the car from one end to the other (long ways). It is often used to describe the layout of the engine and powertrain. For example, front-wheel drive vehicles may have a longitudinally-mounted engine or a transverse-mounted engine. Each style has pros and cons.

Image 2: The longitudinal force/direction goes along the length of the car.

Transverse Direction

Transverse is used to describe a direction or force across a vehicle, from side-to-side. Many of the earlier front-wheel drive “econoboxes” had transverse mounted drivetrains with unequal length drive axles. This type of car was cheap to produce but most were later upgraded to more sophisticated (longitudinal based) /drivetrains.

Image 3: A transverse direction or force goes across the width of a car (side-to-side).

Longitudinal / Transverse Drivetrains

Longitudinal – Rear Wheel Drive (RWD)

Image 4: Example of a Longitudinal Drivetrain & Rear Wheel Drive

This is an extremely popular drivetrain configuration from the “Detroit Iron” era. This front engine, rear wheel drive configuration powered almost every vehicle coming out of Detroit for a 100 year span. It is still the most popular powertrain configuration for trucks.

Transverse – Front Wheel Drive (FWD)

Image 5: Example of a front engine / transversely mounted drivetrain

This is a popular layout for front engine / front wheel drive cars with a transversely mounted engine. Many manufacturers used this layout to build “econoboxes”.

Longitudinal / Transverse Controls

The terms longitudinal and transverse are also used to describe forces placed on a car during driving. Longitudinal forces are produced during acceleration and braking with the strongest forces occurring during braking. Transverse forces are placed on the car during cornering. The suspension system is designed with controls for these two forces.

The rear suspension system shown in the image below is from a solid rear axle “Detroit Iron” car. This system uses a Panhard rod (A) to control transverse forces and two trailing arms (B) to control longitudinal forces. So a technician that is diagnosing a clunking noise from the rear of this car while swerving from left to right would focus on the Panhard since it is the transverse control for the rear of this car. A technician that is diagnosing a clunking noise from the rear of this car while accelerating/braking would focus on the two trailing rods (B) since they are the longitudinal controls for the rear of this car.

Image 6: Suspension parts that control against longitudinal and transverse forces

Car Types

StyleDoorsTrunkRoof DesignTowing
Sedan4Yes1FixedYes (Moderate)
Coupe2YesFixed / Removable / FoldingNo
Hatchback3,5No2FixedYes (Moderate)
Convertible2,4YesRemovable / FoldingYes (Moderate)
Station Wagon4No2Fixed3Yes (Moderate)
Pickup Truck2,4NoFixed (High)Yes (Heavy)
Mini Van3,5No2Fixed (High)Yes (Moderate)
SUV3,5No2Fixed (High)Yes (Moderate)
1 – Accessible from a trunk lid and possible a fold-down rear seat
2 – The luggage area is open to the cabin of the car
3 – The roof stays high to the rear of the car.

Pillar Definitions

The posts that connect the roof to the body of the car are called pillars. In the automotive industry, there is a unified naming scheme. As shown in the image below, the first pillar that goes alongside the windshield is the “A” pillar. The pillars increase one letter in the alphabet from front to rear with one exception. The rear pillar, that goes alongside the rear windshield, will not be below a “C” pillar. Even if a car does not have a physical “B” pillar, it is implied to have one and the back pillar is still the “C” pillar.

Illustration 1: The uniform pillar naming scheme used in the automotive service industry