Tech Talk

The key point of contact between truck and trailer

Safety, stability, improved turning radius and ease of coupling and uncoupling are among the many benefits of a truck’s fifth wheel, but this vital component requires regular maintenance to continue operating safely and effectively.

There aren’t many components on a modern truck that can trace their lineage back to horse-drawn carriages of the mid-1850s, but that’s the case with the fifth wheel, which was adapted for motor vehicles in the early 1900s.

These days it’s near impossible to imagine life without the ease of coupling and uncoupling, not to mention the stability and manoeuvrability afforded by this device. 

But as handy and ingenious as the fifth wheel is, it is not a set and forget component. Far from it, because the fifth wheel is the key point of contact between your rig and trailer, so bears the brunt of the loads you haul, day in and day out.

For this reason, regular and thorough fifth wheel maintenance is essential, to avoid annoying and costly hitching problems, or worse still the nightmare scenario of a trailer disconnecting and becoming a potentially lethal object. Performing basic regular maintenance will help ensure your truck’s fifth wheel remains in good and serviceable condition, and that your fleet continues to run at optimal efficiency.

To find out best practices when it comes to fifth wheel maintenance, we have approached one of the biggest manufacturers, SAF-Holland, for some tips on how to look after your fifth wheel.

FW0E70 fifth wheel.

In the case of SAF-Holland fifth wheels, it is recommended that maintenance is performed every three months or 50,000 kilometres, whichever comes first. The first step in any maintenance procedure is to thoroughly steam clean all components to remove as much of the old dirt, grease and debris as possible. Once the fifth wheel has been cleaned up, inspect the mounting and assembly. Check the fastener torque and look for any bent, worn, broken or missing bolts and other parts. Replace any missing or damaged bolts using genuine SAF- Holland parts available from your nearest PACCAR Dealer, or visit

Check the operation of the locking mechanism by opening and closing the locks with a SAF-Holland Kingpin Lock Tester. Ensure that the nut and washer fit snug against the fifth wheel and that the mechanism locks completely closed around the kingpin.

Once that’s done, use a water-resistant lithium-based grease to grease the trailer contact surface and the bracket supports, as well as the grease nipple for the locks. 

Remember to also lubricate the cam track and pivot with a light oil or diesel oil. On sliding fifth wheels, spray a light oil or diesel oil on the rack and slide path.

The next step is to check your fifth wheel slide adjustments. To do this, first position the truck and trailer in a straight line on level ground, then lock the trailer brakes. 

Release the slide locking plungers, either via the air operated switch in the cab, or the manual release lever on the fifth wheel. Visually check that both plungers are fully extended. If the plungers do not release, raise the trailer to relieve pressure on the plungers. 

This will allow the fifth wheel to slide more easily. Slowly drive the truck forward or backward to position the fifth wheel. Re-engage the slide locking plungers and verify that both plungers have fully engaged.

Remember to avoid using any fifth wheel that is not operating properly. If there is a problem with any aspect of your fifth wheel, contact your nearest PACCAR Dealer for advice.

As chain of responsibility laws bring heightened focus on quality components and maintenance schedules, it is imperative that fifth wheel maintenance is carried out regularly on your truck and trailer fleet. The PACCAR Part Dealer network are experts in trailer maintenance, and many are accredited through quality suppliers like SAF-Holland. For more information or to discuss your trailer and fifth wheel maintenance requirements, contact your local PACCAR Dealer, or visit

Special thanks to Phil Crosbie, national aftermarket manager at SAF Holland Australia who imparted his knowledge to assist with this article.

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