Inspecting Combination Vehicles
The seven-step inspection
A proper pre-trip inspection follows a fixed order: (1) vehicle overview, (2) engine compartment, (3) cab and controls, (4) walk-around inspection, (5) brake check, (6) coupling system check, and (7) trailer check. For combination vehicles, the coupling system and trailer steps deserve extra attention.
What to check on the combination
- Fifth wheel: securely mounted, jaws closed around the kingpin, locking lever engaged, no cracks.
- Kingpin: not bent, worn, or missing.
- Air lines and electrical cord: no cracks, no chafing, proper connection.
- Landing gear: fully raised, crank secured.
- Trailer frame and body: no cracks, no missing lights, mud flaps present.
- Tires: proper inflation, tread depth, no cuts.
- Brakes: slack adjusters, push rods, and air chambers intact.
Traps
- Questions ask you to identify the most important check. For a combination, it is the coupling system - a failed fifth-wheel lock causes a trailer separation.
- Another trap is the order: the brake check comes before the coupling check in the standard sequence.
- Candidates often forget the trailer spring brakes test - with the trailer disconnected, the trailer brakes should lock.
Rule of thumb
If you find a defect in the coupling system, do not drive until it is repaired - no exception.