Gooseneck to 5th Wheel Trailer Coupler Adapter - 25K - Inner Tube - Square - 25K
Heavy-duty square inner tube adapter that converts a gooseneck trailer coupler to a 2" industry-standard king pin for towing with a fifth wheel hitch.
Overview
This gooseneck-to-fifth-wheel adapter is designed to replace the inner tube on most standard 4" square gooseneck couplers and provide a 2" industry-standard king pin connection. It is a practical solution for customers who need to tow a gooseneck trailer with a truck already equipped with a fifth wheel hitch.
R&P Service Insight
Coupler adapters like this are most useful when the trailer and truck are set up with different hitch systems. Before ordering, confirm your outer coupler tube size, pin hole diameter, required adjustment range, and trailer capacity.
- Towing Flexibility: Converts a gooseneck trailer connection for use with a fifth wheel hitch.
- Height Control: The 8" vertical adjustment range helps correct trailer attitude and hookup geometry.
- Heavy-Duty Application: Steel construction and a 25,000 lb rating support demanding trailer use.
R&P Knowledge Hub
Compatibility: Fits most standard 4" square outer gooseneck coupler tubes.
Vehicle / System Fit: For gooseneck trailers being towed by trucks equipped with a fifth wheel hitch instead of a bed-mounted gooseneck ball.
Installation Notes: Uses 13/16" pin holes and requires a compatible load-bearing pin such as GCPN-PIN, sold separately.
Performance Insight: Proper trailer height helps improve ride quality, towing stability, and overall trailer-to-truck hookup geometry.
Brand & Fitment Note
Selling Brand: R&P Carriages stocked trailer coupler adapter.
Application Reference: This listing describes trailer-side gooseneck-to-fifth-wheel compatibility where tube size, pin hole size, capacity rating, and adjustment requirements match.
What This Means: This listing is for a gooseneck to fifth wheel inner tube adapter with a 2" king pin connection. It is not presented as a vehicle-specific OEM component.
Before Ordering: Verify measurements, outer tube size, pin diameter, required adjustment range, trailer capacity, and included components before installation.
R&P Repair Insight
Adapter fitment depends on matching the trailer’s existing outer coupler tube and pin setup. A correct fit should slide into the outer tube properly, align with the pin holes, and provide enough vertical adjustment to level the trailer.
- Check Tube Size: Confirm your trailer uses a standard 4" square outer gooseneck coupler tube.
- Check Pin Size: This adapter uses 13/16" pin holes and requires a compatible load-bearing pin.
- Check Trailer Height: The 8" adjustment range should be compared against your tow vehicle and trailer ride height before ordering.
Features
Gooseneck to Fifth Wheel Conversion
Converts a gooseneck trailer coupler connection to a 2" industry-standard king pin for use with a fifth wheel hitch.
4" Square Inner Tube Fit
Designed to replace the inner tube on most standard 4" square outer gooseneck coupler tubes.
8" Vertical Adjustment
Adjustable height range helps level the trailer and improve towing geometry across different truck and trailer combinations.
25,000 lb Rated Construction
Heavy-duty steel construction is rated up to 25,000 lbs and is SAE J2638 compliant.
Specifications
| Specification | Detail |
|---|---|
| Part Number | KP5G-Q25IP |
| Product Type | Gooseneck to fifth wheel inner tube adapter |
| Application | Converts a gooseneck trailer coupler for towing with a fifth wheel hitch |
| King Pin | 2" industry-standard king pin |
| Tube Width | 4" |
| Vertical Adjustment Range | 8" |
| Hole Spacing | 2-11/16" center-to-center |
| Pin Hole Diameter | 13/16" |
| Plate Dimensions | 9-7/8" long x 10" wide |
| Overall Length | 34-3/4" |
| Weight Capacity | 25,000 lbs |
| Compliance | SAE J2638 |
Fitment / Application
| Category | Details |
|---|---|
| Trailer System | Gooseneck trailers being towed by trucks equipped with a fifth wheel hitch |
| Primary Fit | Most standard 4" square outer gooseneck coupler tubes |
| Capacity Application | Trailer-side coupler application rated up to 25,000 lbs |
| Notes | Requires a compatible load-bearing pin such as GCPN-PIN, sold separately. Verify tube size, pin hole diameter, and trailer rating before installation. |
Included Components
| Quantity | Item |
|---|---|
| 1 | Gooseneck to fifth wheel square inner tube adapter with 2" industry-standard king pin |
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