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If you’ve got a gooseneck trailer but want to pull it with a fifth wheel hitch, this adapter makes that switch clean and easy. The Gooseneck to 5th Wheel Trailer Coupler Adapter – Round – 30K connects your gooseneck trailer to your fifth wheel setup without extra hardware or complicated modifications. It fits most standard 4" round gooseneck outer tubes and gives you a standard king pin connection so it locks solidly into the hitch jaws.
This heavy-duty coupler adapter is built to handle big loads. With a 30,000-lb weight capacity and .275" wall thickness on the inner tube, it’s a tough piece of gear for heavy equipment, livestock, or large trailers. The welded belly band around the lower section adds structural reinforcement for extra strength under full load.
Getting your trailer level is key for safe towing. The adapter has an 8" range of vertical adjustment with holes spaced 2-11/16" center-to-center, so you can dial in the right height for your setup. The overall tube length is 29" from top to plate, with the first adjustment hole 14" down from the top. That flexibility makes it easy to match your trailer to your fifth wheel hitch height.
Made from sturdy steel and tested to SAE J2638 standards, this adapter gives you a reliable fit and secure pull every time. The round inner tube slides into your existing gooseneck outer tube and locks in place with a load-bearing safety pin (sold separately). The plate measures 9-7/8" long by 10" wide, offering a stable platform for your fifth wheel king pin connection.
To protect your hitch head and keep things quiet during travel, you can use a standard 10" lube plate with this adapter. It helps reduce friction and wear between the hitch and the adapter plate so your setup stays smooth and long-lasting.
Customer Satisfaction Score:
99% were satisfied with this product
1% of customers were not satisfied
Ratings & Reviews
Prompt delivery. Have not towed with the adapter yet, but product appears to be very heavy duty with thick walled pipe and very sturdy welds. I am anxious to test it.
This product allows me to use a fifth wheel hitch to haul my 34' camper trailer and quickly convert to haul my 35' gooseneck trailer with my tractor and implements.
It worked just fine. but it rusted being out in the weather attached to the trailer. I'm going to clean it and paint it hopefully to make it last. I do like it and it made it easy to back the truck up to the trailer.
It is heavy duty well made. I have it as a backup for my different trucks, so have not needed it yet. I have no doubt it will meet all expectations
Well built product, easy installation and price was good compared to some of the others. I'm very happy and satisfied with it.
Product is very good. Best part is the etrailer website. Very intuitive and easy to use. Super easy to track product. This is the most well thought out and executed website I have ever used.
Package arrived in some what good condition all products were undamaged shipper (UPS) dosent handle your products with care !
With shipping that fast I’ll never get my trailer parts from anyone else!
I ordered the part on a weekend and it arrived within 5 days. I was able to install and the product is holding up very well. I will be ordering more parts from e trailer for sure
Amazing build and great design. This think is thick!
Very excited to see how much better the 34 foot cargo trailer will be with this conversion.
Product works great
Works great
Brady
12/24/2025
Still working perfect. Has been several miles zero issues
Lazer S.
12/24/2025
Product was delivered as advertised. After cleaning and painting, the adapter looks like the trailer was designed with it. Now I can tow my 5th wheel camper and my gooseneck trailer without removing my hitch. A lot easier for me!
I am extremely happy with this fifth wheel adapter, works great, was delivered in a timely manner
Well built for the price. Had to get one to take my class A cdl test, but now I can haul my 40' gooseneck trailer with any truck.
The part I ordered showed up sooner than promised! Thank you!
fits as should
Worked out good. Easy to install.
The adapter makes the trailer too high in the front due to the height of the fifth wheel hitch.
Great craftsmanship on the adapter, works perfect. Will save my back not having to pull out 5th wheel hitch every time I need to switch to pulling a different trailer. Overall experience was excellent. Great prices, awesome customer service and fast delivery time.
I have 3 of them. They are a good product and they are built very well. I recommend them to anyone who wants to convert to a 5th wheel! etrailer is a Great Company to deal with! Take Care!’
Great product. Allowed me to use a friends gooseneck trailer with my fifth wheel hitch and haul 4 tons of wood pellets! Very easy to put on and take off.
This may be a compatibility issue between manufacturers, but why is the front of the hitch pin plate not centered with the trailer center
Jenny N.
5/29/2024
To be honest we have asked our manufacturers this question before however we have not gotten a definitive answer. We do know that it does not effect the performance.
Great product. Could have been packed better for shipping. No packing and wasn’t going to hurt my product but probably did some damage to other packages and box was tore up.
Converted my gooseneck to a fifth wheel with this adapter everything was super simple
Kevin F.
1/20/2026
This piece is extremely sturdy and strong. I’ve put 3 electric hummers on my trailer and this piece along with my axles of the trailer support the weight well.
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Richard K.
4/30/2018
I could not be more pleased with my kingpin adapter. It exceeds all my expectations and makes the conversion a simple process. My brother and me farm together and he is very impressed with the adapter. Others I have shown it to agree. I keep your site bookmarked for future reference.