How to Turn Your Gooseneck Trailer into a Fifth Wheel

How to Turn Your Gooseneck Trailer into a Fifth Wheel
PopUp GN5 king pin adapter connected to fifth wheel hitch receiver

When it comes to pulling the heaviest trailers with a pickup, you’re likely going to need a fifth wheel or gooseneck hitch to maximize towing capability. But it can be difficult and time consuming if you have to swap out hitches when you change trailer types, as we found out last year during one of our tests. For this situation, we used a PopUp GN5 gooseneck-to-fifth-wheel trailer adapter.

With the GN5 adapter, it took us less than two minutes to modify a gooseneck Cimarron horse trailer so it would work with a fifth wheel hitch.

Before we describe how it works, though, here’s a quick primer on the difference between heavy trailer hitch types.

Bulldog gooseneck hitch

A fifth-wheel or gooseneck hitch relocates the point of truck-to-trailer contact from the conventional rear bumper position to a more centralized spot in the truck's cargo box, most often over the rear axle. This places a larger portion of the mass of a heavier trailer onto the truck’s suspension, via the trailer’s tongue or king pin.

If you’ve ever ridden in a heavy-duty pickup and commented about the stiff ride, such as with a GM or Ram 2500 or 3500 rig or a Ford F-250 or F-350, now you understand why. These trucks are designed to handle a heavy trailer, with the load either handled by a weight-distributing hitch or a fifth-wheel attached directly to the frame.

Even though they function similarly, gooseneck and fifth wheel hitches use very different hardware. A fifth-wheel receiver looks like a giant horseshoe. It’s the same style of device you’ll find on the back of an 18-wheeler semi. A gooseneck hitch looks like a conventional trailer receiver ball mounted on a plate in the bed.

PopUp GN5 fifth wheel adapter (left) and Bulldog gooseneck hitch (right)

In the case of our Cimarron trailer, its hitch featured an open housing that allowed us to slide out a Bulldog gooseneck coupler and slide in the GN5 fifth wheel adapter, so we could hook up the Cimarron to the fifth wheel in the back of the truck we were testing. Since the GN5 was machined with four holes, we could adjust its height to align perfectly with the fifth wheel hitch in the back of the truck. It’s sturdy, too, weighing in at about 41 pounds.

The best part? Having the GN5 on hand meant we could tow both the Cimarron gooseneck and a Dutchmen fifth-wheel RV without having to swap out cargo box receivers. It costs about $160, but that’s money well spent on time saved.



Is that your brawny frame we see in the last pic Mike? Thought you guys had interns for that sort of thing. LOL

Good post - this is something that truck people forget but that new truck owners really, really appreciate learning.

@Jason: If I could patent my genome, I'd be sitting on a beach in the Caribbean instead of hacking in front of a computer all day. That said, I like to get my hands dirty every chance I get. :-)

Good story, Mike!

Now, how about one about the hardware needed to go from a Fifth Wheel trailer to a Goose Neck mount?

Nice! Mike, any plans to still do a story on 5th wheel dollies, and how they compare to pulling the same trailer on the regular 5th wheel hitch?

@Alex, @Buy American or say Bye to America!: We've got more stories like this coming soon. Love the idea about the fifth wheel dolly. Kent Sundling from brought his during the 2010 HD Shootout. Made maneuvering his trailer so much easier.

nice story mike! i wasnt aware they made that piece. always good to learn new stuff.

Great story!

I knew they had 5th wheel to GN adapters but I have never seen a GN to 5th wheel.

how about doing some reviews such as this one?

Comparison lesson from my father - who drove trucks professionally for over 50 years combined. Fifth-wheel hitches give the front of the trailer lateral support, meaning the tow truck helps the trailer combat sway in corners and wind. The gooseneck ball flexes more. One is better for on-road. The other is better for off road. Best of both worlds is a fifth-wheel hitch that has adjustable mechanism for flex (as do US Army trucks).

Mike is this available in Australia?, as I know people who tow very large Horse trailers with a Gooseneck, would love to swap to 5th Wheel hitch so they can tow a large 5ver.
Like this 40ft one

the guys over at four wheeler have a simular artical about changing a fifth wheel trailer into a goose neck.

Nice write up Mike. Appreciate the info - and nice to see that such a conversion piece exists. Will gladly pass this along!

Does the GN5 have holes for the pin? I see that it has the 4 holes on the front for the screw, but was wondering about the pin, that goes through.

PopUp Towing Products replacement 2 5/16" gooseneck coupler (GN8A) self-latches and releases remotely with a cable which may be conveniently located near your trailer jack handle. It's molded hitching guide makes for easy coupling.

Hi Mike
I have a General Coach 5th wheel 80's model with a WH switch over the sink area in the galley. I see your Wheel Hitch explained but my manual does not describe this switch. When turned on it turns red. I thought it might me water heater but I don't want to play with it in case it's something else. Can u help me? I have the conversion option.

this is exactly what i want for my gooseneck trailer so i live in bc ca were can i buy one

Can you get this in Oklahoma?

Cool read about gooseneck trailers. I actually didn't know that a gooseneck and a fifth wheel hitch were very different. My brother has been actually thinking of getting a trailer, so maybe reading this article could be beneficial to him.

I am afraid the when I put my fifthwheel hitch in truck it will be about 1 foot higher then my ball on my gooseneck hitch. How do you over come this

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