76 Section 1 Introduction to Collision Repair
Copyright Goodheart-Willcox Co., Inc.
Side Impact
Figure 4-39 shows a unibody hit on the side of
the front fender. Both lower unirails have moved. Inter-
estingly, the rail on the side opposite the impact has
the most damage. A side hit at the cowl is shown in
Figure 4-40. This type of hit causes a lateral force on
the rocker panel, door, fender, and unirails, resulting in
a longitudinal force on the cowl. Notice how the door
protrudes out at the top. This indicates that the cowl is
out of alignment. The windshield was cracked by the
movement of the windshield pillar. You should suspect
damage along the entire width of the cowl.
Figure 4-41 shows a side impact at the center
pillar. The vehicle has sidesway damage. Notice how
the movement of the center pillar pushed up on the
roof. The rocker panel and floor are buckled.
Rear Impact
Figure 4-42A shows a unibody vehicle that was
struck on the rear bumper. The impact force was
spread out over the two rear unirails, causing them
to collapse. The rear body panel, the trunk floor
Figure 4-42B, and both quarter panels are buckled.
The gap at the rear of the door is overlapped. This
vehicle has both mash and sidesway damage.
A light rear impact is shown in Figure 4-43. The
vehicle was hit with enough force to damage the
bumper mounts, rear body panel, and rear unirails. The
damage does not extend to the trunk floor.
Top Impact
As in a full-frame rollover, the amount of damage
sustained by a unibody rollover depends on the
surface the vehicle lands on and the type of rollover.
A rollover can cause damage to the lower frame rails.
Twist damage can also result. Figure 4-44 shows roof
damage on a unibody vehicle caused by a fallen tree.
The downward movement of the front of the roof pulled
the sides of the roof in.
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Figure 4-39. This unibody vehicle was hit on right
front. The right unirail was pushed upward. Both right
and left unirails were pushed to the left. The damage
to the left unirail was more extensive than the damage
to the right unirail.
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Figure 4-41. This unibody vehicle was hit hard in the
center pillar. The damage extends into the roof, rocker
panel, and floor.
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Figure 4-40. This vehicle suffered a lateral hit at the
cowl. This type of damage can be difficult to repair.