An older trailer is confirmed to have no spring parking brakes; its emergency application depends on stored reservoir air. Why are wheel chocks important when that trailer is parked?
Correct answer: The stored air can leak away and stop holding the brakes applied.
On the specifically described non-spring-brake trailer, emergency braking lasts only while sufficient stored air remains. Chocks provide necessary protection against movement as that air leaks away; no manufacturing-date exemption is being tested.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.2.8 - Trailer Service, Parking and Emergency Brakes; printed 6-6, physical 92; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A combination's air pressure appears stable with the service brakes released. A large leak becomes evident when the driver applies them. Which conclusion is justified?
Correct answer: A service-line leak may become apparent only when that circuit is pressurized.
The manual warns that a major service-line leak may not be noticed until braking. The earlier released-brake observation is not sufficient proof that the system is sound; a large loss requires correction, not acceptance.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.2.8 - Trailer Service, Parking and Emergency Brakes; printed 6-6, physical 92; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
The semitrailer has working ABS, but the tractor has no ABS. Which limitation must the driver understand?
Correct answer: Trailer ABS does not prevent the tractor's wheels from locking or the tractor from jackknifing.
ABS on the trailer can reduce brake-induced trailer swing, but it does not equip the tractor with antilock control. The driver must understand the actual combination and its limits; this question gives no universal emergency brake-release recipe.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.3.2 - Braking with ABS; printed 6-7, physical 93; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A driver trained on one conventional fifth wheel is assigned a different low-lube design. Its maker's coupling instructions differ from the generic handbook sequence. What is the proper preparation?
Correct answer: Learn and follow the instructions for that actual coupling and tractor-trailer setup.
Section 6.4 explicitly says rigs differ. Use the actual equipment instructions and training; for example, not every fifth-wheel design is intended to lift the trailer during coupling.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.4 - Coupling and Uncoupling, introduction; printed 6-7, physical 93; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. Equipment qualification: JOST LT SK37W-01 Rev.D, Operation Instructions for JSK 37UW Low Lube and 3CN Series, physical/printed 1; https://jostinternational.com/hubfs/Jost_International_April_2024/Pdf/jsk3cn-operation-instructions.pdf?hsLang=en#page=1. ↗
A conventional fifth-wheel plate requires grease under its manufacturer's instructions, but its working surface has been allowed to run dry. What handling concern can result?
Correct answer: Excess friction between tractor and trailer can interfere with steering.
Where lubrication is required, insufficient lubrication can increase friction between tractor and trailer and cause steering problems. This does not prescribe greasing low-lube liners or give a maintenance procedure for every design.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.4.1 - Coupling Tractor-Semitrailers: Step 1, Inspect Fifth Wheel; printed 6-7, physical 93; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
Before coupling a conventional tractor-semitrailer, the driver finds that the trailer kingpin is visibly bent. The fifth-wheel opening is large enough to accept it. What is the sound decision?
Correct answer: Keep the unit out of service until the coupling defect is corrected.
A kingpin must not be bent or broken. Being able to fit into an opening does not establish a safe lock; do not attempt to force a defective coupling together.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.4.1 - Coupling Tractor-Semitrailers: Step 1, continuation; printed 6-8, physical 94; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A conventional tractor is noticeably angled to a semitrailer before backing under it. Why does the manual call for straight alignment instead?
Correct answer: Angled contact can push the trailer sideways and damage its landing gear.
The handbook's conventional coupling sequence calls for direct alignment because angled backing can force the trailer sideways and damage the supports. Follow the actual equipment procedure rather than use impact to realign it.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.4.1 - Coupling Tractor-Semitrailers: Step 3, Position Tractor; printed 6-8, physical 94; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
After a conventional fifth-wheel coupling attempt, the driver sees daylight between the mating upper and lower plates. A locking sound was heard. How should the visible gap be treated?
Correct answer: As evidence of an improper coupling that must be corrected before travel.
The mating plates should have no visible gap in the conventional coupling described. A gap can mean the kingpin is improperly positioned, including above closed jaws; sound alone does not establish a secure connection.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.4.1 - Coupling Tractor-Semitrailers: Step 13, Inspect Coupling; printed 6-8, physical 94; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A tractor passes the gentle pull check prescribed for its conventional fifth wheel. The driver has not yet completed the required visual inspection. What does the pull-check result establish?
Correct answer: It is only part of verification; the specified visual lock checks are still necessary.
A pull check does not replace inspection of the actual lock and mating surfaces. Secure the vehicle as prescribed before inspecting, and follow the equipment's complete procedure; the handbook's order is not universal across manufacturers.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.4.1 - Coupling Tractor-Semitrailers: Steps 11-13; Step 13 continues on printed 6-9; printed 6-8, physical 94; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. Manufacturer corroboration: JOST LT SK37W-01 Rev.D, physical/printed 2 (pull check plus visual inspection); SAF-HOLLAND ELI-te Coupling Technology, Technology Advantages (visual inspection before tug), https://safholland.com/us/en/technology/technologyCategory/fifth-wheels/eli-te-coupling-technology; both reviewed September 13, 2026. ↗
In a secured conventional fifth-wheel inspection, the lock appears to be gripping the enlarged head at the kingpin's bottom instead of the narrower shank. Which assessment is correct?
Correct answer: The engagement is wrong; the jaws must lock around the shank.
Figure 6.8 identifies the kingpin's head and shank, and the inspection text requires the jaws around the shank, not the head. A reassuring handle position does not excuse the wrong engagement.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.5.1 - Additional Things to Check during a Walk-around Inspection: Coupling System Areas; Figure 6.8; printed 6-10, physical 96; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A combination's hoses and cable look undamaged, but they are stretched nearly tight with the tractor and trailer straight. Which inspection concern remains?
Correct answer: They need enough safely supported slack for turns without snagging or contacting moving parts.
Air and electrical connections must remain protected as the rig articulates. Check adequate turning slack and secure routing together; excessive loose line near moving parts is not the solution.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.5.1 - Additional Things to Check during a Walk-around Inspection: Air and electric lines to trailer; printed 6-10, physical 96; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
On a tractor with a sliding fifth wheel, the control has been returned to its locked setting, but one locking pin is visibly not engaged. May the control position alone be accepted as proof of securement?
Correct answer: No; all required locking pins must be present and fully engaged.
The inspection requires the sliding fifth wheel's locking pins to be present and locked. A control setting is not proof that the mechanism engaged; do not travel with an unresolved slider-lock defect.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.5.1 - Additional Things to Check during a Walk-around Inspection: Sliding fifth wheel; printed 6-10, physical 96; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A semitrailer's front weight is now fully supported by the tractor, with the landing gear raised. Which additional clearance check belongs in the departure inspection?
Correct answer: Check tire-to-trailer-nose and tractor-frame-to-landing-gear clearance, including room for turns.
With the trailer supported in its travel position, verify the specified tire-to-nose and frame-to-landing-gear clearances. The rig must articulate without those components contacting one another.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.4.1 - Coupling Tractor-Semitrailers: Step 15, Raise Front Trailer Supports; printed 6-9, physical 95; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A driver is choosing where to leave a semitrailer. One space appears flat, but its soft surface may not support the landing gear under the trailer's weight. Which assessment is sound?
Correct answer: Ground support must be verified; level appearance alone is not enough.
A suitable uncoupling surface must support the trailer, and its supports must be sound. Level appearance alone is not enough. This is a site-assessment question, not a sequence for releasing a trailer.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.4.2 - Uncoupling Tractor-Semitrailers: Step 1, Position Rig; support check continues on printed 6-10; printed 6-9, physical 95; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A trailer has hydraulically powered landing gear. During its secured inspection, fresh hydraulic leakage is visible even though the supports are fully raised. What conclusion is appropriate?
Correct answer: The powered landing gear still has a defect requiring attention before use.
The landing-gear inspection includes absence of air or hydraulic leakage when power-operated. The supports being raised does not cancel that condition check; follow the equipment's defect and repair procedure.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System; Section 6 - Combination Vehicles; 6.5.1 - Additional Things to Check during a Walk-around Inspection: Landing Gear, continuation; printed 6-11, physical 97; Version: July 2014. Current NCDMV-linked copy reviewed September 13, 2026. ↗
