If you cannot locate the OEM pin box manufacturer's name and model number of your trailer's 5th wheel king pin box, you can measure it to find a correct replacement.
First, select the pin box style from the drawings below that matches the pin box on your 5th wheel trailer.
Next, after you have selected your pin box style, "Click" on the drawing below that matches it. Then print out the drawing and take it to your trailer. Use the drawing to measure the horizontal bolt hole distance, vertical bolt hole distance, bolt size, bolt head size, front row of bolts to king pin, back row of bolts to king pin and pin box width. Also, record the number of bolts per side that secure the pin box to the trailer frame.
Click on your pin box style to access a printable full size drawing.
Click to Enlarge
Finally, use the pin box measurement chart to match the measurements of your trailer's OEM pin box to the manufacturer and model number. This will be the proper replacement pin box for your 5th wheel.
Note: Extending a pin box increases the amount of leverage applied to the frame of a 5th wheel trailer. Because this increased leverage can cause damage to a trailer frame, trailer manufacturers might not honor the trailer warranty if the pin box has been extended. Check with your trailer manufacturer if a new pin box will add more than 6" to the length of your original.
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