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Chapter 3 Vehicle Construction
Drive Train Orientation
Another way to classify vehicles is by drive train orien-
tation, Figure 3-3. The vehicle’s drive train produces
power and conveys this power to the drive wheels. In
most vehicles, a gasoline or diesel engine produces the
power. Although there are a few mid-engine vehicles,
most vehicles have their engines mounted in the front.
Most rear-wheel drive vehicles have a front-mounted
engine that is mounted longitudinally (crankshaft center- r r
line is parallel to the vehicle centerline). See Figure 3-3A.
The engine powers the rear wheels. In a front-wheel drive
vehicle, the engine mounted transversely (crankshaft
centerline is perpendicular to the vehicle centerline),
Figure 3-3B, and powers the front wheels. As its name
implies, a four-wheel drive vehicle powers all four wheels.
See Figure 3-3C. The engine in a four-wheel drive vehicle
can be mounted longitudinally or transversely.
A new type of drive train configuration is a gaso-
line/electric hybrid. A hybrid vehicle is powered by a
transversely mounted gasoline engine and an electric
motor. The gas engine is relatively small, making it more
fuel-efficient than a larger engine. Because the small
gasoline engine is not very powerful, the electric motor
assists the engine when more power is needed. There
are two types of hybrids. A parallel hybrid, or full hybrid,
can be powered by the gas engine only, the electric
motor only, or both at the same time. In a series hybrid,
or mild hybrid, the electric motor assists the gasoline
engine during acceleration or going up a hill, but the
electric motor alone does not power the vehicle.
Body Styles
Body styles are often taken into consideration when
classifying vehicles, Figure 3-4. A vehicle’s body style
is determined by the configuration of its body panels.
A typical sedan is shown in Figure 3-4A. A sedan can
have two doors or four doors. The window glass in each
door is surrounded by a channel. There is a pillar behind
each front door. The doors close against these pillars.
A coupe is a two-door vehicle that does not have a
channel surrounding the window glass. The coupe has
a pillar behind each front door. See Figure 3-4B.
A station wagon has four doors and a roof that
extends to the rear of the vehicle, enclosing the cargo
area behind the back seat. A rear door provides access
to the cargo area. This area is also accessible through
the passenger compartment. Figure 3-4C shows a
station wagon. A hatchback, Figure 3-4D, usually has
two doors and a lift gate that allows access to the trunk
Transmission
Engine
Drive shaft
Differential
A C B
Rear drive
axle
Axle shaft
Engine
Transaxle
Dead axle
Engine
Front drive
axles
Front
differential
Transmission
Transfer
case
Drive
shaft
Drive
shaft
Rear drive
axles Rear
differential
Figure 3-3. Vehicles are commonly classified by drive train configuration. A—Rear wheel drive vehicle. B—Front wheel
drive vehicle. C—Four-wheel drive vehicle.