A 5th wheel king pin box for a gooseneck hitch is a specialized adapter that allows a 5th wheel trailer—originally designed to connect to a 5th wheel hitch in the bed of a pickup truck—to be towed using a gooseneck hitch instead. Here's a detailed breakdown of its function and use:

🔧 What It Is

A 5th wheel king pin box for gooseneck hitch is a conversion adapter that replaces or attaches to the standard king pin box of a 5th wheel trailer. It modifies the connection point so that the trailer can be hitched directly to a gooseneck ball in the truck bed, rather than a traditional 5th wheel hitch.

🛠️ How It Works

• The gooseneck adapter bolts to the trailer’s existing 5th wheel mounting points or replaces the OEM king pin box entirely.
• Instead of a king pin that slides into a 5th wheel hitch, the adapter provides a coupler that locks onto the 2 5/16" gooseneck ball in the truck bed.
• Some models (like Reese Goose Box or Gen-Y Executive) incorporate built-in suspension and shock absorption systems to help smooth the ride.

✅ Advantages

• Bed Space Savings: Gooseneck hitches are usually smaller and lower-profile than 5th wheel hitches, leaving more usable truck bed space when not towing.
• Easier Disconnect: Many gooseneck setups are simpler to couple/uncouple than traditional 5th wheel hitches.
• Cost-Effective: For truck owners who already have a gooseneck hitch installed (commonly used for horse trailers, flatbeds, etc.), this avoids the need to install a separate 5th wheel hitch.
• DOT-Approved Options: Many high-end adapters are tested and approved for highway use and maintain warranty compliance.

⚠️ Considerations

• Frame Stress: Some solid (non-flexing) adapters may transfer more stress to the trailer frame, which can void warranties unless the adapter is an OEM-approved replacement (like the Reese Goose Box).
• Height Adjustability: Make sure the gooseneck adapter you choose has adequate height adjustment to keep your trailer level.
• Weight Ratings: Always check the GTWR (Gross Trailer Weight Rating) and pin weight capacity of the adapter to match your trailer’s specs.

🏁 Conclusion

A 5th wheel king pin box for a gooseneck hitch offers a smart and flexible solution for truck owners who want to tow a 5th wheel trailer without installing a bulky 5th wheel hitch. Whether you’re aiming to maximize truck bed space, streamline your towing setup, or leverage an existing gooseneck hitch, these adapters provide a practical path forward. However, it’s essential to choose a model that aligns with your trailer’s weight specifications and your manufacturer’s warranty requirements. With the right adapter, you can enjoy the benefits of both towing systems—without compromise.