Vehicle Body, Chassis and Frame
What the exam tests
This domain tests body construction, chassis and frame layout, collision energy management, panel alignment, corrosion protection and safe body repair.
Core rules
- Body-on-frame construction uses a separate ladder frame; monocoque or unibody construction uses the body shell as the load-bearing structure.
- Crumple zones deform to absorb impact energy; the passenger cell is reinforced to protect occupants. Never straighten or weld a crumple zone without following repair specifications.
- Chassis checks include frame straightness, crossmember condition, suspension mounts, weld integrity and corrosion.
- After body repair, restore sealers, cavity wax and paint; bare steel rusts quickly.
- Use correct PPE when welding, grinding or handling sealers; galvanised metal produces harmful fumes when heated.
Worked example
A car has uneven panel gaps and a pull after a front-end impact. Reasoning: check frame and suspension mounting points with a measuring system before replacing panels. Uneven gaps may indicate body distortion rather than poor hinge adjustment. Repair structure first, then align panels, then apply corrosion protection and paint. Skipping measurement can leave hidden safety damage.
Traps that cost marks
Covering rust with body filler, welding without eye and fume protection, ignoring hidden structural damage, and using heat on high-strength steel without approval.