DESIGN EVOLUTION
Not too long ago, nearly every ear and truck built in Amer-
ica was built with body-over-frame construction, rear-
wheel drive, and symmetrical designs. Today, most cars
do not have a separate frame; instead, the frame and body
are built as a single unit, called a unibody. In 1977, When
most ears were built on a Frame, the average weight of a
ear Was 4,500 pounds ( 16,800 kg). Today, because of unibody construction and changes in materials, the average
weight is 3,000 pounds (1,120 kg). Most tiueks are still
built on a frame.
Another major influence on design was the switch
from rear-wheel drive to front-wheel diive. Making this