Fifth-Wheel Hitches and Hitch Ratings

Unlike travel-trailer hitches, which are broken out into classes, fifth-wheel hitches are simply designated by the maximum weight of the trailer they are designed to tow

By Chris Hemer / Photos by Bob Livingston

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f you’re new to RVing, or perhaps have considered moving up to a larger trailer, you’ve probably thought about a fifth wheel and may have wondered how these larger models differ from their travel trailer counterparts. Fifth wheels typically represent a much larger investment in both the trailer and the tow vehicle, so it’s a good idea to learn about what equipment is required to tow them.

Prepping the Truck
It wasn’t long ago that a fifth wheel represented the ultimate commitment in towing. Unlike a travel trailer hitch — which simply slides into a receiver already on the tow vehicle — a fifth-wheel hitch required that a structure first be fabricated and attached to the truck’s frame for mounting the hitch. So, in addition to the cost of the hitch itself, there were often significant labor charges involved — and hopefully the technician you trusted with the job did it correctly. Later, aftermarket kits were made for various models of trucks to simplify the process. Still, sometimes the truck bed had to be disconnected and raised for the installation.

Finally, the “Big Three” automakers (Ford, General Motors and Fiat Chrysler) recognized that preparing a truck for fifth-wheel towing was not only very inconvenient for its customers but also costly, and began offering “fifth wheel ready” packages with all the structural work already completed at the factory level. Later, factory-installed “puck” mounting systems emerged with the holes already drilled in the bed and sockets incorporated into the frame rails designed to accept unique fasteners. These have become the go-to choice in fifth wheel set-ups — in fact, industry sources estimate that half of all Ram 2500 and 3500 trucks are ordered from the factory with a puck mounting system because it simplifies the hitch installation tremendously. Just line up the hitch in the truck bed, lock the fasteners in place and you’re good to tow.So, if you anticipate purchasing a new truck to haul a fifth wheel, it will be worth your while to opt for a fifth-wheel ready model.

PullRite mounting kit includes the rails for securing the SuperGlide sliding hitch and all the necessary brackets and hardware.

Before preparing and bolting the rail brackets to the frame, you’ll have to do some precise measuring. PullRite’s installation instructions show exactly where holes need to be drilled, which will take some study to make sure the measurements are correct. It’s one of those “measure twice, drill once” projects, and mistakes can be messy.

Before crawling under the truck to install the brackets, the spare tire and metal shield will have to be removed to provide access to the frame.

Hitch Types
Some truck manufacturers also offer models already outfitted with a fifth-wheel hitch, which may be a consideration if you just want to finance the whole thing, connect the trailer and head down the road. However, it’s still a good idea to shop the variety of hitch systems available to make sure you select the one that best fits your individual needs. Fifth wheel hitches continue to evolve and range from the basic up to high-end models that may incorporate air bags, high-density foam cells or other features designed to make towing smoother and more comfortable. Still others can be quickly broken down in different sections, making installation/removal easier for one person.

Unlike travel trailer hitches, which are broken out into classes, fifth-wheel hitches are simply designated by the maximum weight of the trailer (gross trailer weight) they are designed to tow. A 16,000-pound (or “16K”) hitch is rated for up to 16,000 pounds gross trailer weight; a 20K hitch is designed for a gross trailer weight of up to 20,000 pounds, and so on. Because you won’t necessarily know the weight of your trailer when it’s full of fresh water, LP-gas and supplies, it’s always a good idea to base your hitch purchase on the trailer’s gross vehicle weight rating (GVWR) and purchase the next-highest-rated model. For example, if your trailer has a GVWR of 18,000 pounds, go with a 20k hitch. It won’t cost much more and will you give you added capacity. Also, consider the future: You may want to trade for a larger fifth wheel, which may require a higher-rated hitch.

In most cases, fifth wheels are pulled by full-size, heavy duty (3/4 or 1-ton) trucks with 8-foot beds, so there is adequate room for the front of the trailer (called the “cap”) to clear the cab of the truck when navigating a sharp turn (around 90 degrees). However, a fifth wheel can also be towed by a heavy-duty truck with a 6-foot bed using the right equipment. For short-bed applications, hitch manufacturers have designed an automatic sliding or “slider” hitch, which moves rearward when the truck and trailer reach a certain turn angle. Automatic sliding hitches are more costly, but much cheaper than repairing your truck and trailer after the front cap and cab crash into one another. More on this later.

Fortunately, service center technicians can use a template provided by PullRite, which speeds up the measuring process and helps prevent mistakes

Once the technician is sure that the template is positioned correctly, pilot holes are drilled through the truck bed

(4a) Fortunately, service center technicians can use a template provided by PullRite, which speeds up the measuring process and helps prevent mistakes. Still, the template must be placed correctly to ensure that the bolt holes will line up with the frame brackets. (4b) Once the technician is sure that the template is positioned correctly, pilot holes are drilled through the truck bed.

A 1/8-inch tab is located below each slotted bolt hole in the front brackets and is pryed open to allow the flange nuts to be inserted before pushing the tab back into position. This tab helps hold the flange nut in place when bolting the bracket to the frame.

Spacers are also added to the front brackets to insure a good fit. This is when experience comes into play. The installer had the instructions memorized; first-timers will be spending some time reading — and re-reading — the instructions to ensure a correct installation.

Another option for short bed trucks is a pin box extension mounted on the trailer, which bolts to the existing pin box structure. These incorporate a locking wedge that prevents the fifth wheel hitch from turning; instead, the extension features a rotating turret that moves the pivot point 22 inches rearward. Essentially, it performs the same function as an automatic sliding fifth wheel hitch — it’s just a different way of doing things and costs about the same. Pin boxes are also available in different weight ratings and some even offer a suspension system of some kind to absorb road shock. Just make sure that the hitch you own (or are considering) is compatible with a pin box extension, because not all of them are.

Another option that’s out there are gooseneck adaptors. Gooseneck hitches are a heavy-duty option for cargo and livestock trailers. Goosenecks are more challenging, as a rule, to connect than fifth wheels because of the precise positioning needed for the connection. While there are gooseneck adaptors of various kinds on the market, as a rule, they should be approached by RVers with extreme caution. Gooseneck adaptors change the stress factors on the trailer frame and have been connected to fifth-wheel frame and sidewall fractures which will not be covered under many RV manufacturer warranties. Those interested in using a gooseneck adaptor must contact their trailer and chassis manufacturers to get the OK to use a gooseneck adaptor before installing one.

After drilling all the holes in the bed, the brackets are bolted to the frame, which takes patience and a double-jointed body. The process would be easier if there were no fuel tank and drive shaft to contend with, but that’s where experience shines. There’s no drilling in the truck frame since all the bolts go into factory holes — the only way this can work without major undercarriage disassembly. Brackets should not be fully tightened at this time to allow for some wiggle room when lining up the bolts through the bedrails.

Bolts are test fitted through the truck bed and frame brackets to make sure they can be threaded into the flange nuts

(8a) A step bit is used to drill the bolt holes through the bed, which is recommended by PullRite. (8b) Bolts are test fitted through the truck bed and frame brackets to make sure they can be threaded into the flange nuts.

After confirming that the bolt holes are correct, the front rail is bolted into place. Base rail spacers are used to prevent crushing the corrugated truck bed when tightening the bolts.

A 1 1/8-inch hole must be drilled through the truck bed (only) to allow the 4-inch base rail bolt to pass through the bottom of the cross sill and top of the oblong hole in the rear frame bracket

Lining up the holes through the truck bed and rear brackets is not an exact science. Here, a larger drill bit was used to shave enough metal to line up the bolt holes.

(10a) A 1 1/8-inch hole must be drilled through the truck bed (only) to allow the 4-inch base rail bolt to pass through the bottom of the cross sill and top of the oblong hole in the rear frame bracket. This is done for both brackets. (10b) Lining up the holes through the truck bed and rear brackets is not an exact science. Here, a larger drill bit was used to shave enough metal to line up the bolt holes.

Adjusting Trailer Height
Both the pin box on the trailer and the fifth wheel hitch are adjustable for height, which can be particularly important on taller heavy-duty trucks. If the trailer is in too much of a “nose up” position when hitched, it can limit the amount of clearance between the lower, front section portion of the trailer (the part above the hitch saddle) and the bed rail/tailgate of the truck. This can cause interference problems on steep driveways or other road undulations. Such a position also shifts an abundance of trailer weight to the rear axle, possibly overloading it and the tires on that axle. Also, the rear portion of the fifth wheel can drag on the ground when negotiating driveways and dips in the road.

When correctly adjusted, the truck and trailer should be level and there should be a minimum of 6 inches between the fifth wheel cabover and the truck bed rail. If, on the other hand, the truck is still too tall for the trailer (i.e., a lifted four-wheel-drive vehicle towing a toy hauler), there are still some options. The truck can be lowered through different wheel/tire combinations, suspension adjustments, or both — or the trailer can be raised. So called suspension “flip kits” place the trailer’s leaf springs above the axles instead of below them, netting a lift of several inches. A common misconception is that raising the trailer will make it top heavy or change its handling characteristics, but from our experience, a few inches won’t make an appreciable difference. Where there is a possible concern is the overall height of the trailer (which includes air-conditioning units, satellite antennas or anything else mounted to the roof). While there is no federal height requirement, most states have height limits starting at 13 feet, 6 inches, and as high as 14 feet, according to the Federal Highway Administration. Some exceptions are granted for lower clearance on particular local roads that may have low bridges, but those are marked. As a general rule, it’s best to stay below 13 feet, 6 inches in overall height.

The bed channel spacer tubes dropped in nicely after the holes were cleaned up. Once completed, the remaining bolts in the rear bed rail were only snugged.

The base rail foot assemblies are pinned into the bed rails in their respective positions. The pins can be removed if the owner wants to pull out the hitch.

Fifth-wheel hitches are fairly heavy and will require two people to position on the rails. Therefore, it’s best to place the box with the hitch components, which is easier to handle, on the end of the truck bed first before removing the hitch from the box and placing it in the base rail foot assemblies.

The hitch is placed into the base rail assemblies and bolts are hand tightened. Some technicians may elect to bolt the base rail assemblies to the hitch first, but the method used here seemed to work best.

Adjusting the threaded stop will remove excessive play between the Cam Slot and Turntable Cam Arm Roller. This is first done by hand until it is difficult to move the arm roller in the cam slot. Tightening the jam nut with a wrench secures the threaded stop.

The plate assembly is then secured to the rocker arm using clevis pins and clips.

If you own a ¾- or 1-ton truck that was not prepped for fifth-wheel towing, there’s no need to purchase another truck. A fifth-wheel subframe can still be installed on your existing truck, after which you can install the fifth-wheel hitch system of your choosing. Such was the case with a certain 2021 Ram 2500 short-bed pick up, which we followed during installation of a fifth-wheel hitch. The owner ordered the truck without fifth-wheel prep, then later decided to enter the fifth-wheel fray. The frame brackets and mounting rails were installed at Mike Thompson’s RV Super Stores, Colton, Calif., by a highly qualified mechanic, so the truck was ready for just about any fifth-wheel hitch.

Since this is a short bed truck, the owner chose the performance and convenience of an automatic sliding hitch by PullRite. PullRite wrote the book on automatic sliders and its line of SuperGlide hitches is rated to tow up to 16,000, 20,000 or 24,000 pounds. While universal rails are available for just about any truck, PullRite’s 20K Industry Standard Rail Custom Mounting Kit (part #2746; $499) was installed before affixing the company’s 20K SuperGlide automatic sliding hitch (part #2900; $1,899). PullRite makes installation easier by providing all necessary brackets, hardware and instructions, and even offers a template to make determining the hitch location easier.

Bolts holding the hitch to the base rail foot assemblies are torqued to 75 ft.-lbs. after initial tightening with an impact wrench

(17a) Once the hitch is secure, the truck bed rail and frame bracket bolts are tightened to spec. By only snugging the fasteners first, the tech has some wiggle room when piecing together all the components. (17b) Bolts holding the hitch to the base rail foot assemblies are torqued to 75 ft.-lbs. after initial tightening with an impact wrench.

The hitch occupies a good portion of the bed. All the components are well-built and powder-coated for protection against the elements. The only required maintenance is to keep the moving components clean and treated with WD-40.

As the truck turns, the plate assembly and turntable roll on the way tubes, pulling the mechanism back enough for the front of the fifth wheel to clear the back of truck cab

(19a) The capture plate is attached to the kingpin box and secured using bolts in the front and back. The plate is needed to lock the kingpin box onto the hitch plate assembly. (19b) As the truck turns, the plate assembly and turntable roll on the way tubes, pulling the mechanism back enough for the front of the fifth wheel to clear the back of truck cab.

Capture plates are matched to the kingpin box and are ordered separately from the dealer or online.

Sources:

Mike Thompson’s RV Super Store (Colton, CA)
(909) 318-2175
mikethompson.com

Pulliam Enterprises, Inc./PullRite
(800) 443-2307
pullrite.com

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