Common Issues With Fifth Wheel Hitches and How To Fix Them

Anyone who owns a semi-truck and hauls heavy loads knows how important of a component the fifth wheel hitch is. This hardware attaches to the trailer kingpin and enables the rig to turn safely. If the hitch were to break or malfunction, it could cause issues ranging from minor steering difficulties to more serious accidents or trailer separation.

If you've been noticing subtle signs your fifth wheel hitch is starting to fail, like excessive noise or difficulty locking, let's look at some of the more common issues with these couplers and what you can do to fix them before they progress.

Excessive Friction and Dry Lube Plates

Metal grinding against metal creates heat and wear that no trucker wants to deal with. A fifth wheel plate needs a barrier between itself and the trailer apron to articulate smoothly during turns. When that barrier disappears, you'll hear groaning or screeching noises whenever the rig turns a corner. You might also feel resistance in the steering wheel because the trailer doesn't want to rotate freely on the hitch.

You can solve this pretty easily. If you use a greased fifth wheel, scrape off the old, gritty gunk and apply a fresh layer of high-quality lithium grease. For those who prefer lube plates, you should inspect the plastic disk for cracks, thinning, or missing sections. Replacing a worn-out lube plate costs very little and protects the expensive top plate from permanent damage.

Worn Jaw Mechanisms

The jaws are the parts that actually grab the kingpin and hold the trailer to the truck. Over time, the constant pulling and pushing forces of hauling loads will wear down the steel surfaces of the locking jaws. You'll notice this as "slop" or excess play in the connection. It feels like a distinct clunk or bump when you accelerate from a stop or apply the brakes.

Most modern fifth wheels have an adjustment mechanism to compensate for some wear. You can locate an adjustment screw on the side of the hitch that tightens the jaw's grip on the kingpin. You'll want to follow the manufacturer's specs closely here so you don't over-tighten it. If the adjustment screw is maxed out and there's still play, you'll need to buy a jaw replacement kit. Swapping out the jaws restores the tight connection you need for a smooth ride.

Bent or Jammed Release Handles

Drivers pull the release handle thousands of times over the life of a truck. Sometimes, that handle gets bent, either from manual force or from debris striking it. A bent handle might bind up against the side of the hitch or the frame, which makes uncoupling the trailer extremely difficult or impossible. You might see the metal rod curving at an odd angle, or it just won't slide in and out smoothly.

You might feel tempted to grab a hammer and bang it back into shape. While that works in a pinch, metal fatigue sets in when you bend steel back and forth. A weakened handle could snap off later when you're trying to drop a load. The safer repair involves purchasing a replacement handle kit. Installing a new rod allows the mechanism to operate freely and prevents you from getting stuck attached to a trailer you're trying to drop.

Cracked Top Plate

The top plate takes the weight of the trailer and transfers it to the truck's axles. Fatigue, overloading, or accidents can cause stress cracks in the cast steel structure. These cracks usually form near the throat of the hitch or around the mounting pin bosses. A cracked plate poses a severe safety risk because the metal has lost its structural integrity.

You can’t fix a cracked top plate with a welder. Welding on these heat-treated casting changes the metal's properties and often makes it brittle, which leads to catastrophic failure. If you find a crack during your pre-trip inspection, the truck needs to come out of service immediately. You have to replace the entire top plate assembly. It's an investment, but it's the only way to restore the safety rating of the vehicle.

Worn Pivot Pins and Bushings

The fifth wheel needs to tilt forward and backward to handle uneven terrain and ramps. Steel pins ride inside rubber or polyurethane bushings to allow this articulation. When these bushings wear out, metal starts hitting metal. You'll hear loud banging noises when going over bumps, and you might see uneven tire wear on the steer axle because the trailer isn't sitting stable.

You can check this by using a pry bar to lift the fifth wheel plate. If it moves up and down significantly on the mounts, the bushings are toast. Rebuild kits are available that include new pins, bushings, and retaining hardware. Installing new bushings restores the cushion between the hitch and the mounts, which smooths out the ride and protects the frame from shock damage.

Severe Corrosion and Rust

Rust never sleeps, especially if your routes take you through the salt belt during winter. Corrosion creates pits in the metal surface and can seize up the moving parts of the locking mechanism. If the safety latch or the cam gets stuck due to rust, you might think you're coupled securely when you aren't.

Fighting rust requires regular attention. You should steam clean the hitch periodically to remove salty road spray. If rust has already taken hold, using a wire brush or sandblaster to clean the mechanism helps. Once you've got it down to bare metal, applying a fresh coat of paint and lubricating all moving parts helps protect it. If a part is too corroded to move freely even after cleaning, you'll need to swap it out for a new one.

Damaged Trailer Kingpin

Sometimes the problem isn't the hitch itself, but the partner it's trying to dance with. A bent or worn kingpin on the trailer can cause all sorts of issues for your fifth wheel. A damaged pin can chew up the locking jaws, prevent the mechanism from latching, or cause binding during turns.

You should use a kingpin gauge to check for straightness and proper length. If the gauge doesn't fit, the pin is out of spec. A trailer repair shop needs to cut out the old kingpin and weld in a new one. While this is a trailer repair, fixing it saves your fifth wheel from premature destruction. It takes two to tango, and both parts of the coupling need to be in good shape for a safe journey.

Keep Your Rig Rolling

Understanding what the most common issues with fifth wheel hitches are, and how you can fix them, can help you prevent more serious and more costly mechanical problems with your rig. At Higgs Parts, we sell fifth wheel replacement parts to make repairing issues like bent handles, worn jaws, and rusty latches quick, affordable, and easy. Shop our selection of spacers, rails, washers, and bolts, among other products, and buy what you need to get your truck functional again.