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Coupling Inspection and Maintenance

Being the literal point of connection to your tow vehicle, coupling is critical. Here’s a run-through of coupling maintenance that will keep yours in good nick.

We can almost hear the sighs. Another thing to maintain — how important can it be, really? The answer is extremely important. While backup safety features do exist, you simply wouldn’t want to be relying on those should your rig ever detach from your tow vehicle. Consider the possible outcomes of that particular scenario, and the importance of coupling maintenance is crystal-clear from the outset. 

There is a range of couplings floating around in the market, but here we’ll stick with what is by far the most popular type — the ball coupling. 

Andrew Phillips from The RV Repair Centre takes us through a step-by-step how-to for basic torque checks and adjustments that a competent layperson should be able to undertake. There is nothing overly technical here, but again, this is not something to be done by halves. If you’re in doubt, please contact a licensed professional for assistance.

1. Coupling attachment to A-frame

The coupling is generally secured to the A-frame by welded-on bolts under the coupling plate. The nuts need to be checked for tightness with a torque wrench — Andrew advises 150Nm. The coupling assembly, A-frame and fasteners should also be thoroughly inspected for any signs of excessive corrosion, cracks or other abnormalities that could cause the coupling to detach from the A-frame.

2. Apply grease to plunger

Applying grease to the plunger will ensure it operates more smoothly, is protected against corrosion, and most importantly will be easier for the coupling to engage on the ball.

3. Apply grease inside coupling cavity

Applying a light film of grease inside the coupling cavity will reduce wear, minimise corrosion, and make the coupling/uncoupling process a little easier. 

4. Attach coupling on tow ball to adjust fitment

The ball and/or coupling can wear over time, creating excessive play, and the adjusting screw/lock nut can become loose. The first step to check for this is to attach the coupling to the tow ball. This check will need to be done on level concrete with the van park brake off and safety chains attached. 

5. Use adjusting screw to tighten or loosen coupling fit to ball

Loosen the adjusting screw lock nut. Tighten the adjusting screw until it just stops (while holding the lock nut still). Loosen the adjusting screw the minimum amount, which will enable the coupling to be detached from the ball using the jockey wheel. Note: overtightening the adjusting screw can cause wear to the screw and the ball or cause the screw to break — you may have to trial this adjustment a few times until you get it right. Once adjusted, hold the adjusting screw in position and tighten the locking nut. Recheck that the coupling can be attached and detached from the ball. Further note: this adjustment procedure will not compensate for an incorrectly sized or excessively worn ball or coupling. If in doubt, consult a licensed professional.

Thanks to Andrew Phillips and his team at the RV Repair Centre:
120 Canterbury Rd
Bayswater Nth VIC 3151
Ph: (03) 9761 4189

Improper maintenance could lead to injury, death, or property damage. Maintenance work of this nature should only be undertaken by persons with suitable mechanical competence. If in doubt, consult a licensed professional. Information provided is general in nature and can only be taken as a guide. Individual discretion must be exercised and persons undertaking described tasks do so completely at their own risk. Publishers and creators of this content accept no responsibility for loss or damage.


  • Peter Hannah: June 08, 2022

    Interesting reading. Thanks.

    We have lived on the road for 10 years now, and it is really interesting the 99% of people who think – that applying a small amount of grease to the towball prior to connecting your trailer or van – is a sin!

    “Lubrication is better than “Aggravation” – was a statement I received when we first connected our caravan (home) for the first time. You can always wipe it off and re-lube the ball. Once dust and grime start degrading the towball and coupling – the cost outweighs the benefits by miles.

  • Peter Edwards: June 08, 2022

    Grease is an excellent medium for retaining sand and dust particles. When you apply grease to the tow hitch cavity, then add sand and dust, you have a wonderful grinding compound, which can possibly wear through the metal components just as effectively as dry, un-lubricated metal to metal contact.

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