71 Chapter 4 Fundamentals of Collision Damage
Copyright Goodheart-Willcox Co., Inc.
members in the center section of the vehicle no longer
form a rectangle. The distorted area is shaped like a
diamond.
As any of these front impacts are taking place,
inertia can be involved. Again, consider a truck
involved in a front impact. If the target is solid and
unyielding so the truck stops in an instant, the bed
could deflect upward, causing dents in the back of
the cab. If the inertia is great enough, the frame will
buckle. The buckle in the frame will usually be found
under the cab. This type of damage may be deceiving.
It may look as if the truck is bent down under the
cab. Actually, the rear suspension mount is distorted
upward. This makes the center of the vehicle sit closer
to the ground. The same is true in a frontal impact that
distorts the front suspension mounts upward. The front
suspension is higher than normal, again causing the
center of the truck to sit closer to the ground. If the
frame rails under the cab are not level with each other,
the damage is called twist. A severe front impact can
cause twist in the frame.
As a frame rail or cross member moves during a
collision, attached parts may also be damaged. Parts
that can be damaged by a front impact include the
front axle assembly, front suspension, exhaust mani-
fold, starter, transfer case, transmission, body or cab
mounts, floor, and cowl. If a door does not fit properly,
you should suspect cowl damage.
Side Impact
A side impact at the front of a full-frame vehicle
may cause one or both frame rails to move. This type
of damage is sidesway. If the frame is impacted as
shown in Figure 4-28, part of the impact force will
cause a buckle in the right frame rail. The rest of the
impact force will be transferred by the front cross
member to the left frame rail. If the cross member is
weak and the left frame rail has enough strength to
resist the force, the cross member will buckle and the
left frame rail will not be damaged. If the left frame rail
cannot resist the force, the cross member and both
frame rails will be damaged.
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Figure 4-26. The impact between the frame rails
caused the rails to move toward each other.
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Figure 4-25. An impact on the right front of the vehicle
caused these buckles in the frame rails. The engine
cross member/front suspension mount served as a
pivot point.
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Figure 4-27. An impact on the right frame rail caused
the rail to move back compared to the left rail.
Diamond damage is present when the center section
of the vehicle is not square.