Understanding Excessive Fifth Wheel Play
What causes it, how to spot it, and what to do next
Published on
May 21, 2025 at 10:05:41 AM PDT May 21, 2025 at 10:05:41 AM PDTst, May 21, 2025 at 10:05:41 AM PDT
Fifth wheel play is something most drivers notice before they fully understand. Maybe the trailer feels loose when braking. Maybe there’s a banging sound on takeoff. These small signs of instability often point to the same issue: excessive movement between the trailer kingpin and the fifth wheel locking mechanism.
And while a little play is normal — even engineered into most coupling systems — too much play can lead to uneven wear and long-term damage to your coupling components that can result in part failure. This guide covers what excessive play is, how to spot it, what causes it, and what you can do to fix it.
What Is Excessive Fifth Wheel Play and Why It Matters
Fifth wheel “play” or “slop” refers to unwanted movement or slack between the fifth wheel assembly and the trailer’s kingpin. A small amount of movement is normal. In fact, it’s necessary to allow the trailer to pivot during turns and adjust to uneven road surfaces. But when that play exceeds design tolerances, it starts to create real problems.
Excessive play can lead to:
Slop, jolting, or lurching during starts, stops, and turns.
Uneven or accelerated wear on fifth wheel lock jaws.
Premature kingpin and fifth wheel damage.
Inconsistent or failed locking engagement.
Added stress on mounting components, brackets, and bushings.
Per SAF-HOLLAND product manuals, many fifth wheels are built to allow 1/8" to 1/4" of lateral or fore-aft movement when the kingpin is properly secured, depending on the specific model. Movement beyond those limits is commonly a sign of worn lock jaws, an undersized/worn kingpin, or improper fitment between the two.
Catching excessive play early allows for simpler repairs and helps protect the rest of the trailer and tractor system from unnecessary wear. Ignoring it can lead to larger repairs, compliance issues, and, in extreme cases, part failure that can cause highway accidents.
How to Identify Excessive Play
Recognizing excessive fifth wheel play starts with paying attention to how the trailer behaves and following that up with a proper inspection. For many drivers and technicians, the warning signs show up during normal operation, but confirming the cause requires a close look at the coupling mechanism itself.
The Impact on Other Parts & Components
Excessive fifth wheel play isn’t just a coupling problem. It has ripple effects across your tractor-trailer system. That unwanted movement between the kingpin and the lock jaws doesn’t stay isolated. It can create stress and wear in places that weren’t designed to absorb it.
Suspension and Mounting Systems
When the trailer shifts unexpectedly during turns or braking, that force can be transferred into the suspension and mounting components. Over time, this increases wear on:
Fifth wheel mounting brackets and bolts.
Pivot bushings and slide tracks.
Trailer suspension components.
Steering and Braking Performance
A misaligned or loose fifth wheel connection can throw off the balance between the tractor and trailer. That affects both handling and stopping consistency, particularly under load. Drivers may notice:
Delayed or uneven braking response.
Steering that feels off-center, especially during turns or lane changes.
Extra trailer sway on uneven roads or in crosswinds.
Fixing the Problem: Adjusting or Repairing the Fifth Wheel Lock
Once excessive play has been confirmed, the next step is determining whether the issue lies with the fifth wheel, the kingpin, or both. Repairs may involve replacing lock jaws, adjusting internal components, or installing a rebuild kit. If the parts are in good shape and working order, excessive movement may also be corrected through adjustment of the fifth wheel’s locking mechanism.
Locking Mechanism Adjustments
Most modern fifth wheels include some form of built-in adjustability. These features are designed to compensate for minor wear on the lock jaws over time, helping extend service life and maintain tight coupling without requiring full replacement. Note that tension adjustments should never be made to compensate for excessive wear found on the trailer kingpin.
The adjustment process is typically done during regular preventative maintenance while using a lock tester tool to check for gaps and looseness in the coupling mechanism. The exact method for adjusting the tension will depend on your specific fifth wheel brand and model, so review your owner’s manual for guidance. Typically, you can make precise adjustments by turning a screw, nut, or rod/wedge mechanism located on the side or bottom of the top plate.
Key Considerations Before Making Repairs:
Verify manufacturer tolerances for play: Each fifth wheel model has its own spec for acceptable movement in the locking mechanism, usually 1/8” or 1/4”. Compare your measurements to those found in your product manual.
Check both sides of the coupler: New locking jaws won't solve the problem if the kingpin is worn, and vice versa. Evaluate the coupling system as a whole, not just the most visible component.
Use compatible parts: Make sure that replacement jaws, kingpins, and other components match the fifth wheel model and are rated for the trailer’s load class.
Consider rebuild kits: Many OEM and aftermarket brands offer rebuild kits that allow for replacement of wear components like lock jaws without having to replace the entire fifth wheel assembly. However, these should only be installed if the fifth wheel is good condition with no structural damage.
Important! Adjustments to the locking mechanism should never be used to compensate for parts with wear or damage that exceeds safe operating limits. If the lock jaws or kingpin is severely worn, replacing the part or rebuilding the fifth assembly is the only safe option.
Shop Fifth Wheel & Kingpin Parts That Fit
Get high-quality replacements that meet or exceed OEM standards.
Excessive fifth wheel play can sneak up on even the best-maintained trucks. But when it shows up, it could be a sign that something deeper is wearing out. If your coupling feels sloppy, makes noise, or doesn't lock in as tight as it used to, it’s worth taking a closer look.
When replacement is needed, fitment is everything. At JIT Truck Parts, we stock aftermarket fifth wheel assemblies, rebuild kits, and trailer kingpins that meet or exceed OEM standards.