Fifth Wheel and Coupling System Inspection
The advanced pre-trip inspection for combination vehicles requires careful attention to the coupling system beyond what is covered in basic CDL training. Begin the fifth wheel inspection by verifying that the plate is properly lubricated — dry or cracked grease indicates the fifth wheel is overdue for service and can accelerate wear on both the fifth wheel plate and the trailer apron. Rock the plate fore and aft to check for excessive play in the mounting pivot; more than one inch of movement indicates loose mounting bolts or a worn pivot pin. Inspect the jaws and release mechanism by looking through the opening in the fifth wheel from the driver's side: the jaws should be fully closed around the kingpin with no visible gap. Pull the release handle firmly — it should require deliberate force to pull out, not slide freely. A freely sliding release handle indicates a broken or missing return spring, a serious safety defect. For sliding fifth wheel tractors, count the number of locking pins (typically 2 or 4) and verify each pin is fully seated in the slide rail hole. Missing or partially engaged pins will allow the fifth wheel to shift forward under braking, drastically changing the vehicle's weight distribution and handling characteristics.