CDL General Knowledge TestCombination Vehicles (if applicable)Hard
A driver notices significant 'chucking' or surging when accelerating or decelerating a combination vehicle. What is the most likely cause?
- AOver-inflated air bags on the trailer suspension.
- BWorn or loose kingpin and/or fifth wheel assembly.
- CImproper tire pressure on the drive axles.
- DInsufficient lubrication in the wheel bearings.
Show answer & explanationAnswer & explanation
Correct answer: B. Worn or loose kingpin and/or fifth wheel assembly.
Chucking or surging is often caused by excessive play between the tractor and trailer, which is typically due to a worn or loose kingpin and/or fifth wheel assembly. This allows the trailer to move independently of the tractor during acceleration and deceleration.
Why the other options are wrong
- A. Over-inflated air bags would result in a harsher ride, but not the specific surging motion described as chucking.
- C. Improper tire pressure can affect handling and fuel efficiency, but is unlikely to cause chucking.
- D. Insufficient wheel bearing lubrication would cause overheating or wheel lock-up, not chucking.
Chucking/Surging Cause
Chucking or surging in a combination vehicle is usually caused by excessive play or wear in the kingpin and/or fifth wheel connection, leading to independent movement between tractor and trailer.
- Feels like a push/pull motion.
- Occurs during acceleration/deceleration.
- Indicates loose connection.
- Inspect kingpin and fifth wheel.
Memory trick: Loose link, rough ride.