Trailer couplings are a critical component of any caravan or trailer set-up so ensuring they are correctly maintained is essential for a safe and efficient towing experience. 

In this Cruisemasterclass, we'll discuss the correct maintenance techniques for trailer couplings, with a particular focus on the Cruisemaster DO35 and the DO45 couplings. However, many of the principles we discuss will apply to other couplings on the market.

Cruisemasterclass Episode 13: Coupling Maintenance

Pre-Trip Maintenance

Before heading off on any trip, it's important to give your coupling a thorough visual inspection. This should include checking for any missing bolts, damage to components and signs of wear. 

Next ensure that all components are secured and nothing is loose by giving everything a gentle wiggle. Make sure you also check your tow pin to ensure it is secured tightly to the tow vehicle. 

Checking your couplings locking mechanism is also vital, especially if you've been operating in dirty or muddy conditions. Make sure it's free from any contaminants, heavy grease, and other debris, and ensure it has that positive click when connected. 

While looking for contamination, you should also check your tow pin, making sure it's not heavily gummed up with grease or debris.

Servicing Coupling Maintenance Checks

As part of your caravan or trailers regular servicing, the first thing to do is to feel for any play in your couplings bushes. Check both vertically, sideways, and in/out. 

If excessive play is found, you will need to knock the roll pin out of the back of the coupling to allow access to tighten the nut. Depending on the trailers drawbar construction, this may be a bit tricky, but most roll pins can be removed with a pin punch.

Replacing Coupling Bushes

If tightening the nut doesn't fix the excessive play, you may need to replace your bushes. To do this, knock your roll pin out, unscrew the nut off the back of the coupling, and slide the housing off the yoke. You will find a bush at the front that needs to be slid off the back and a bush in the back of the housing.

Once you have removed the old bushes, you will need to replace them with new ones, reassemble the coupling, and slide the housing back on. You may need to pull the housing back a bit to get the nut on because there is a lot of room between the handbrake and the back of the yoke. 

Once the nut is done up, replace the roll pin, and use grease on the bushes to pre-lubricate them before sticking them in.

The Cruisemaster DO-35 V3 plus coupling utilizes two identical round bushes, available in the Replacement DO35 V3 Spindle Bush Kit. However, on other couplings, bush sizes may vary. 

With multiple DO-35 coupling versions, we have a cheat sheet that allows you to identify your coupling and which spare parts you'll need which can be found on our DO35 Identifier page.

Greasing Trailer Couplings

Once you have fully assembled the coupling, you will need to grease it, using a grease gun. Stick the grease gun on the grease nipple on the side of the coupling and give it a pump. Grease should be added until it starts to come out the sides of the coupling, indicating it is full.

Below is an illustration that breaks down the key components of the Cruisemaster DO35 and their locations. 

We use a standard lithium bearing grease which doesn't affect the bushes. Using the wrong type of grease can damage the bushes, so be careful and make sure the grease is compatible.

Tow Pin Maintenance

Tow pin maintenance is reasonably easy, with the priority to make sure that everything is tight and torqued. You can also use a light smear of grease around the polyurethane bush of the tow pin to help prevent any pre-mature wear.

For more caravan and towing tips, make sure to keep an eye out for the latest episodes of our Cruisemasterclass series by subscribing to the Cruisemaster YouTube channel and following us on Facebook & Instagram.